# Treatment of mixed connective tissue disease: A multicenter retrospective study

Kevin Chevalier, Benjamin Thoreau, Marc Michel, Bertrand Godeau, Christian Agard, Thomas Papo, Karim Sacre, Raphaèle Seror, Xavier Mariette, Patrice Cacoub, et al.

<figure><img src="image_1.png" /></figure>

## To cite this version:

Kevin Chevalier, Benjamin Thoreau, Marc Michel, Bertrand Godeau, Christian Agard, et al. Treatment of mixed connective tissue disease: A multicenter retrospective study. Journal of Autoimmunity, 2025, 153, pp.103420. 10.1016/j.jaut.2025.103420. hal-05038629

HAL Id: hal-05038629

https://u-picardie.hal.science/hal-05038629v1

Submitted on 27 May 2025

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

# Treatment of mixed connective tissue disease: A multicenter retrospective study

Kevin Chevalier<sup>a,●</sup>, Benjamin Thoreau<sup>a</sup>, Marc Michel<sup>b</sup>, Bertrand Godeau<sup>b</sup>, Christian Agard<sup>c</sup>, Thomas Papo<sup>d</sup>, Karim Sacre<sup>d</sup>, Raphaèle Seror<sup>e,f</sup>, Xavier Mariette<sup>e,f</sup>, Patrice Cacoub<sup>g</sup>, Ygal Benhamou<sup>h</sup>, Hervé Levesque<sup>h</sup>, Cécile Goujard<sup>i</sup>, Olivier Lambotte<sup>i</sup>, Bernard Bonnotte<sup>j</sup>, Maxime Samson<sup>j</sup>, Félix Ackermann<sup>k</sup>, Jean Schmidt<sup>l</sup>, Pierre Duhaut<sup>l</sup>, Kahn Jean-Emmanuel<sup>m</sup>, Thomas Hanslik<sup>m</sup>, Nathalie Costedoat-Chalumeau<sup>a</sup>, Benjamin Terrier<sup>a</sup>, Alexis Regent<sup>a</sup>, Bertrand Dunogue<sup>a</sup>, Pascal Cohen<sup>a</sup>, Véronique LE. Guern<sup>a</sup>, Eric Hachulla<sup>n</sup>, Benjamin Chaigne<sup>a,1</sup>, Luc Mouthon<sup>a,*,1</sup>

## ARTICLE INFO

Handling editor: C Selmi

**Keywords:**

Disease-modifying antirheumatic drugs

Glucocorticoids

Hydroxychloroquine

Immunosuppressant

Interstitial lung disease

Mixed connective tissue disease

Pulmonary arterial hypertension

## ABSTRACT

**Introduction:** Mixed connective tissue disease (MCTD) is a rare systemic disorder that belongs to connective tissue diseases (CTD). Few studies are available on MCTD treatment.

**Methods:** We conducted an observational study within the French MCTD cohort. Data were collected at diagnosis, during follow-up, and at the last follow-up (LFU). We studied three treatment groups i) no treatment, ii) hydroxychloroquine (HCQ) and/or glucocorticoids (GC) and iii) disease-modifying antirheumatic drugs (DMARDs)/immunosuppressant (IS).

**Results:** Three hundred and fifteen patients were included and followed for 96 [40–156] months. At MCTD diagnosis, 52 (16.5 %) patients were treatment-free, while 224 (71.1 %) received GC and/or HCQ and 39 (12.4 %) received DMARDs and/or IS. During follow-up, 10 (3.2 %) patients remained treatment-free, and 77 (24.4 %) were GC-free. Most patients (n = 271; 85.8 %) received HCQ, and 161 (51.1 %) were treated with DMARDs and/or IS. DMARDs and/or IS, including anti-B cell therapeutics, were more frequently prescribed in patients with musculoskeletal involvement (p < 0.0001), interstitial lung disease (ILD, p < 0.0001) and/or pulmonary arterial hypertension (PAH, p < 0.01). Patients in clinical remission and those who did not evolve to a differentiated CTD (MCTD-dCTD) received significantly less frequently DMARDs and/or IS (including anti-B cell therapeutics; p <

<footnote><sup>a</sup> Department of Internal Medicine, National Reference Center for Rare Systemic Autoimmune Diseases and Autoinflammatory Diseases of Ile de France, East and West, Hôpital Cochin, Assistance Publique-Hôpitaux de Paris (APHP), Université Paris Cité, Paris, France</footnote>

<footnote><sup>b</sup> Department of Internal Medicine, Henri-Mondor University Hospital, APHP, Université Paris Est Créteil (UPEC), Créteil, France</footnote>

<footnote><sup>c</sup> Department of Internal Medicine, Nantes Université, CHU Nantes, Service de Médecine Interne, F-44000, Nantes, France</footnote>

<footnote><sup>d</sup> Department of Internal Medicine, Hôpital Bichat-Claude Bernard, APHP, Université Paris Cité, France</footnote>

<footnote><sup>e</sup> Department of Rheumatology, National Reference Center for Rare Systemic Autoimmune, AP-HP, Hôpital Bicêtre, Université Paris Saclay, France</footnote>

<footnote><sup>f</sup> Center for Immunology of Viral Infections and Auto-immune Diseases (IMVA), INSERM UMR1184, Le Kremlin-Bicêtre, France</footnote>

<footnote><sup>g</sup> Department of Internal Medicine and Clinical Immunology, Groupe Hospitalier Pitié-Salpêtrière, APHP, Université Paris Sorbonne, Paris, France</footnote>

<footnote><sup>h</sup> Department of Internal Medicine, CHU de Rouen, UniRouen, Rouen, France</footnote>

<footnote><sup>i</sup> Université Paris Saclay, Department of Internal Medicine and Clinical Immunology, Bicêtre Hospital, APHP, UMR1184 Inserm, CEA, Le Kremlin Bicêtre, France</footnote>

<footnote><sup>j</sup> Department of Internal Medicine and Clinical Immunology, Dijon University Hospital, Dijon, France</footnote>

<footnote><sup>k</sup> Department of Internal Medicine, Foch Hospital, Suresnes, France</footnote>

<footnote><sup>l</sup> Department of Internal Medicine and RECIF, Amiens University Hospital, Université Picardie Jules Verne, Amiens, France</footnote>

<footnote><sup>m</sup> Department of Internal Medicine, Ambroise Paré Hospital, APHP, Université de Versailles Saint-Quentin-en-Yvelines, Boulogne-Billancourt, France</footnote>

<footnote><sup>n</sup> Department of Internal Medicine and Clinical Immunology, Referral Centre for Rare Systemic Auto-immune and Auto-inflammatory Diseases North North-West Mediterranean and Guadeloupe (CeRAINOM), Univ. Lille, Inserm, CHU Lille, U1286 – INFINITE, University of Lille, F-59037, Lille, France</footnote>

<footnote>* Corresponding author. Department of Internal Medicine, Reference Center for Rare Systemic Auto Immune and Autoinflammatory Diseases of Ile de France East and West, Cochin University Hospital, Assistance Publique-Hôpitaux de Paris, 27 rue du Faubourg Saint Jacques, 75014, Paris, France.

**E-mail address:** luc.mouthon@aphp.fr (L. Mouthon).</footnote>

<footnote n="1">¹ Both authors contributed equally.</footnote>
0.0001 for both). Patients who received HCQ at MCTD diagnosis appeared to develop less frequently ILD or PAH (p < 0.05).

**Conclusion:** HCQ and GC were the cornerstones of MCTD treatment and were sufficient to control disease manifestations in nearly half of the patients, reflecting the good prognosis of this disease. DMARDs and IS were used for musculoskeletal involvement, PAH/ILD, and in MCTD-dCTD patients.

**Abbreviations**

- Abs antibodies

- ACR American College of Rheumatology

- CI confidence interval

- CK Creatine kinase

- CTD connective tissue disease

- CYC cyclophosphamide

- GC glucocorticoids

- dCTD definite CTDs

- DLCO diffusing capacity of the lungs for carbon monoxide

- DMARDs disease-modifying antirheumatic drugs

- ERN ReCONNET European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases

- EULAR European alliance of associations for rheumatology

- HCQ hydroxychloroquine

- HRCT high resolution computed tomography

- IIM idiopathic inflammatory myopathy

- ILD interstitial lung disease

- IQR interquartile range

- IS immunosuppressant

- LFU last follow-up

- MCTD mixed connective tissue disease

- MCTD-dCTD MCTD who evolved toward a dCTD

- MMF mycophenolate mofetil

- MTX methotrexate

- OR Odds-ratio

- PF pulmonary fibrosis

- PAH Pulmonary arterial hypertension

- RA rheumatoid arthritis

- RTX rituximab

- SLE systemic lupus erythematosus

- SjD Sjögren's disease

- SSc systemic sclerosis

- U1RNP Ribonucleoprotein U1

# 1. Introduction

Mixed connective tissue disease (MCTD, or Sharp syndrome) is an entity belonging to the spectrum of connective tissue diseases (CTD) defined in 1972 by Sharp *et al.* as a syndrome characterized by the presence of autoantibodies (Abs) directed towards ribonucleoprotein U1 (anti-U1RNP) associated with clinical features of other CTD such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc), or idiopathic inflammatory myopathies (IIM) [1] without fulfilling classification criteria for those CTDs. These features include a wide variety of manifestations such as Raynaud's phenomenon, puffy fingers, arthralgia/arthritis, myalgia/myositis, and life-threatening complications such as interstitial lung disease (ILD) or pulmonary arterial hypertension (PAH) and can affect both adults and children [2–5].

Since the first description of the disease, it has been reported that MCTD has a favorable prognosis and responds well to glucocorticoids (GC), which are considered a cornerstone of treatment. Thus, and as in other CTDs, therapeutic management of patients with MCTD relies mostly on GC alone or in combination with antimalarial, mainly hydroxychloroquine (HCQ) or disease-modifying antirheumatic drugs (DMARDs) but without evidence to support it or to assess its impact on disease prognosis. Indeed, despite the confirmation of MCTD as a distinct entity within the CTD spectrum [4], only a limited number of studies are available on treatment of MCTD patients [6–12]. These studies included limited numbers of patients and did not exclude patients with definite CTDs (dCTD) [6–11] and, to our knowledge, no prospective randomized controlled trials have been conducted. Moreover, MCTD patients with ILD or PAH are included in studies about CTD-associated ILD or CTD-associated PAH, but rarely individualized among other CTDs [13–15]. Consequently, since there is no guideline for MCTD treatment, therapeutic management of patients with MCTD is commonly guided by patient's clinical manifestations, the physicians' expertise, and mostly based on recommendations available in other CTDs [16].

Taking advantage of the French MCTD cohort [4], we conducted an

observational study to better describe treatments in MCTD. The aim of this study was to report the treatments used by practitioners in a large cohort of MCTD patients and their impact on disease prognosis.

# 2. Methods

## 2.1. Study design

We conducted an observational retrospective multicenter cohort study within the French MCTD cohort, a retrospective cohort of patient with MCTD followed in 13 rare diseases reference and competence centers in France. Detailed information about the characteristics of this cohort and its formation have been recently reported [4]. Briefly, inclusion criteria for the MCTD cohort required patients to meet, at the time of disease diagnosis, at least one of the four existing MCTD diagnosis classification criteria, namely Sharp [17], Alarcon-Segovia [18], Kahn [19] or Kasukawa criteria [20]. Patients were excluded if, at the onset of the disease, they fulfilled any of the current classification criteria for another CTD, including the American College of Rheumatology (ACR)/European alliance of associations for rheumatology (EULAR) 2019 classification for SLE [21], the ACR/EULAR 2013 classification for SSc [22], the ACR/EULAR 2010 criteria for rheumatoid arthritis (RA) [23], the ACR/EULAR 2017 classification for IIM [24] or the ACR/EULAR 2016 classification for Sjögren's disease (SjD) [25].

## 2.2. Data collection

Data including demographics, date of MCTD diagnosis and first symptoms, clinical, nailfold capillaroscopy, radiological and biological findings (including immunological data) at MCTD onset, during follow-up and at the last known follow-up (LFU), and date of progression to another CTD if applicable were collected. MCTD patients' treatment were also collected at disease diagnosis, during follow-up, and at LFU.

## 2.3. Definitions

We *a priori* defined three treatment groups for each time point (i.e. at
MCTD diagnosis, during follow-up, and LFU): i) the no treatment group, which refers to patients who did not receive antimalarials, GC, DMARDs or immunosuppressant (IS); ii) the GC/HCQ group which refers to patients who were treated with GC and/or HCQ without any DMARDs or IS and iii) the DMARDs/IS groups referring to patients who received at least one DMARDs and/or IS (associated or not with HCQ and/or GC); patients who received intravenous immunoglobulin were included in this last group. Details about the treatments collected and groups are summarized in the Supplementary Table 1.

Progression to a dCTD (i.e., SLE, RA, SSc, IIM, SjD) was defined according to the current classification criteria (see above). Disease remission was defined at the LFU by combining the (i) 2021 definition of remission in SLE (DORIS) [26] (i.e.: a SLEDAI-2K = 0, a Physician Global

Assessment <0.5 (0–3) and treatments with antimalarials, low-dose GC (prednisolone ≤5 mg/day), and/or stable IS including biologics) and (ii) an EUSTAR activity index <2.5 as previously described [27,28].

PAH was defined according to the 2022 European guidelines, as a mean pulmonary artery pressure >20 mmHg at rest, with pulmonary arterial wedge pressure ≤15 mmHg and pulmonary vascular resistance >2 Wood units upon right heart catheterization [29]. ILD was defined by the presence of at least one of the following imaging findings: honey-combing, traction bronchiectasis, ground-glass opacity, or reticulations in chest-high resolution computed tomography (HRCT) scan [30].

<caption>**Table 1**</caption>

Comparison of patients' characteristics at MCTD disease diagnosis according to treatment groups.

<table><thead><tr><th></th><th>All (n = 315)</th><th>No treatment<sup>b</sup> (n = 52)</th><th>HCQ and/or GC (n = 224)</th><th>DMARDs/IS (n = 39)</th><th>p-value</th></tr></thead><tbody><tr><td>Sex (female)</td><td>277 (88)</td><td>44 (84.6)</td><td>199 (88.8)</td><td>34 (87.2)</td><td>0.7</td></tr><tr><td>Age at diagnosis [IQR]</td><td>35 [26–45]</td><td>31.5 [25.5–46]</td><td>35.5 [26–45]</td><td>38 [22–46]</td><td>0.8</td></tr><tr><td><strong>Ethnic group</strong></td><td></td><td></td><td></td><td></td><td>0.2</td></tr><tr><td>Caucasian</td><td>198/311 (63.7)</td><td>39/51 (76.5)</td><td>138/222 (62.2)</td><td>21/38 (55.3)</td><td></td></tr><tr><td>Afro-Caribbean</td><td>92/311 (29.6)</td><td>9/51 (17.6)</td><td>70/222 (31.5)</td><td>13/38 (34.2)</td><td></td></tr><tr><td>Asian</td><td>21/311 (6.8)</td><td>3/51 (5.9)</td><td>14/222 (6.3)</td><td>4/38 (10.5)</td><td></td></tr><tr><td><strong>Clinical findings</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Fever</td><td>26 (8.3)</td><td>2 (3.8)</td><td>20 (8.9)</td><td>4 (10.3)</td><td>0.4</td></tr><tr><td>Raynaud's phenomenon</td><td>286 (90.8)</td><td>49 (94.2)</td><td>205 (91.5)</td><td>32 (82.1)</td><td>0.2</td></tr><tr><td>Puffy fingers</td><td>145 (46)</td><td>29 (55.8)</td><td>103 (46)</td><td>13 (33.3)</td><td>0.1</td></tr><tr><td>Sclerodactyly</td><td>11 (3.5)</td><td>0 (0)</td><td>6 (2.7)</td><td>5 (12.8)</td><td>&lt;0.01</td></tr><tr><td>Arthralgia</td><td>260 (82.5)</td><td>35 (67.3)</td><td>195 (87.1)</td><td>30 (76.9)</td><td>&lt;0.01</td></tr><tr><td>Synovitis</td><td>67 (21.2)</td><td>4 (7.7)</td><td>47 (21)</td><td>16 (41)</td><td>&lt;0.01</td></tr><tr><td>Myalgia</td><td>101 (32.1)</td><td>10 (19.2)</td><td>75 (33.5)</td><td>16 (41)</td><td>0.06</td></tr><tr><td>Seritis (pericarditis/pleuritis)</td><td>18 (5.7)</td><td>1 (1.9)</td><td>15 (6.7)</td><td>2 (5.1)</td><td>0.7</td></tr><tr><td>Gastroesophageal reflux</td><td>48 (15.2)</td><td>10 (19.2)</td><td>34 (15.2)</td><td>4 (10.3)</td><td>0.6</td></tr><tr><td>Renal disease</td><td>7 (2.2)</td><td>1 (1.9)</td><td>6 (2.7)</td><td>0 (0)</td><td>0.8</td></tr><tr><td>Dyspnea</td><td>52 (16.5)</td><td>6 (11.5)</td><td>34 (15.2)</td><td>12 (30.8)</td><td>0.02</td></tr><tr><td>Parotid swelling</td><td>13 (4.1)</td><td>2 (3.8)</td><td>9 (4)</td><td>2 (5.1)</td><td>0.9</td></tr><tr><td>Subjective oral dryness</td><td>44 (14)</td><td>4 (7.5)</td><td>32 (14.3)</td><td>8 (20.5)</td><td>0.2</td></tr><tr><td>Subjective ocular dryness</td><td>29 (9.2)</td><td>5 (9.6)</td><td>18 (8)</td><td>6 (15.4)</td><td>0.3</td></tr><tr><td>Lymphadenopathy</td><td>46 (14.6)</td><td>8 (15.4)</td><td>33 (14.7)</td><td>5 (12.8)</td><td>&gt;0.9</td></tr><tr><td><strong>MCTD complications</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>PAH</td><td>10 (3.2)</td><td>0 (0)</td><td>3 (1.3)</td><td>7 (17.9)</td><td>&lt;0.0001</td></tr><tr><td>ILD</td><td>37 (11.7)</td><td>3 (5.8)</td><td>24 (10.7)</td><td>10 (25.6)</td><td>0.01</td></tr><tr><td>Pulmonary fibrosis</td><td>9 (2.9)</td><td>1 (1.9)</td><td>2 (0.9)</td><td>6 (15.4)</td><td>&lt;0.0001</td></tr><tr><td><strong>Biological findings</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Anemia</td><td>89/282 (31.6)</td><td>9/50 (18)</td><td>68/197 (34.5)</td><td>12/35 (34.3)</td><td>0.07</td></tr><tr><td>Thrombocytopenia</td><td>20/280 (7.1)</td><td>4/50 (8)</td><td>19/196 (9.7)</td><td>0/34 (0)</td><td>0.2</td></tr><tr><td>Leukopenia</td><td>48/281 (17.1)</td><td>11/50 (22)</td><td>32/196 (16.3)</td><td>5/35 (14.3)</td><td>0.6</td></tr><tr><td>Neutropenia</td><td>13/271 (4.8)</td><td>4/49 (8.2)</td><td>9/189 (4.8)</td><td>0/33 (0)</td><td>0.2</td></tr><tr><td>Lymphocytopenia</td><td>76/271 (28)</td><td>10/49 (20.4)</td><td>54/189 (28.6)</td><td>12/33 (36.4)</td><td>0.3</td></tr><tr><td>CK (IU/L)</td><td>133 [59–555]</td><td>64 [38.1–106]</td><td>143 [75–513]</td><td>612.5 [91–1853]</td><td>&lt;0.01</td></tr><tr><td>Hypergammaglobulinemia</td><td>173/211 (82)</td><td>24/32 (75)</td><td>124/153 (81)</td><td>24/26 (92.3)</td><td>0.2</td></tr><tr><td>Proteinuria (g/mmol)</td><td>0 [0–0.01]</td><td>0 [0–0.01]</td><td>0 [0–0.02]</td><td>0 [0–0]</td><td>—</td></tr><tr><td><strong>Autoantibodies</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Anti-U1RNP Abs</td><td>315 (100)</td><td>52 (100)</td><td>224 (100)</td><td>39 (100)</td><td>—</td></tr><tr><td>Anti-dsDNA Abs</td><td>2 (0.6)</td><td>0 (0)</td><td>2 (0.9)</td><td>0 (0)</td><td>—</td></tr><tr><td>Anti-SSA Abs</td><td>50/311 (16.1)</td><td>6/51 (11.8)</td><td>38/221 (17.2)</td><td>6 (15.4)</td><td>0.6</td></tr><tr><td>Anti-SSB Abs</td><td>7/311 (2.3)</td><td>0/51 (0)</td><td>5/221 (2.2)</td><td>2 (5.1)</td><td>0.2</td></tr><tr><td>Anti-Sm Abs</td><td>10/311 (3.2)</td><td>2/51 (3.9)</td><td>5/221 (2.2)</td><td>3 (7.7)</td><td>0.2</td></tr><tr><td><strong>Main paraclinical findings</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Abnormal naifold capillaroscopy<sup>b</sup></td><td>69/149 (46.3)</td><td>15/31 (48.4)</td><td>50/105 (47.6)</td><td>4/13 (30.8)</td><td>0.5</td></tr><tr><td>Myogenic pattern on EMG</td><td>14/44 (31.8)</td><td>1/5 (20)</td><td>7/28 (25)</td><td>6/11 (54.5)</td><td>0.2</td></tr><tr><td>Myositis on muscle biopsy</td><td>16/23 (69.6)</td><td>0/2 (0)</td><td>6/10 (60)</td><td>10/11 (90.9)</td><td>0.06</td></tr><tr><td>Restrictive pattern on PFTs<sup>c</sup></td><td>24/106 (22.6)</td><td>3/20 (15)</td><td>16/71 (22.5)</td><td>5/15 (33.3)</td><td>0.4</td></tr><tr><td>Altered DLCO<sup>d</sup></td><td>50/102 (49)</td><td>11/20 (55)</td><td>31/68 (45.6)</td><td>8/14 (57.1)</td><td>0.5</td></tr></tbody></table>

Data are presented as number (percentage) or median with interquartile range. P-value were calculated using Chi-squared test or Fisher's exact test for qualitative variables and Mann Whitney's test for quantitative variables.

Abs: antibodies; CK: creatine kinase; GC: glucocorticoids; DLCO: diffusing capacity of the lungs for carbon monoxide; DMARDs: disease-modifying antirheumatic drugs, dsDNA: double stranded desoxyribonucleic acid; EMG: electromyogram; HCQ: hydroxychloroquine; ILD: interstitial lung disease; IS: immunosuppressant; ITP: immune thrombocytopenic purpura; IU/L: international unit by liter; MCTD: mixed connective tissue disease; n: number; PAH: pulmonary arterial hypertension; PFTs: pulmonary function tests; RNP: ribonucleoprotein; Sm: Smith.

<footnote>a No treatment indicate the absence of hydroxychloroquine, glucocorticoids, DMARDs or immunosuppressive treatments.</footnote>

<footnote>b Defined by the presence of giant capillaries and/or capillary rarefaction and/or nailfold capillary hemorrhages.</footnote>

<footnote>c Defined by total lung capacity <80 % of theoretical value on pulmonary function tests.</footnote>

<footnote>d Defined by diffusing capacity of the lungs for carbon monoxide <70 % of theoretical value on pulmonary function tests.</footnote>
## 2.4. Ethical approval

The French MCTD cohort study complied with the Declaration of Helsinki and received approval from the French organization dedicated to privacy, technology, and civil rights in France (Commission Nationale de l'Informatique et des Libertés, reference 225396v0). Ethical Review committee approval was granted on January 30, 2022; number AAA-2022-08008.

## 2.5. Statistical analyses

Data were reported as numbers (n) and percentages (%) for categorical variables, compared using the Chi-square or Fisher's exact test as appropriate. Quantitative variables were expressed as median and interquartile range [IQR] and compared using the Mann Whitney's or Kruskal-Wallis test as appropriate. We considered two-tailed p values under 0.05 to be significant. Logistic regression was used to assess the association between treatments and complications, results were expressed as odds-ratio (OR) and confidence interval (CI). A sensitivity analysis was performed to assess the robustness of the results using 1:1 matching based on a propensity score which included the following parameters: sex, age at MCTD diagnosis, ethnicity, follow-up duration, Raynaud's phenomenon, swollen fingers, arthralgia and myalgia. Missing values were imputed using decision tree methodology. Propensity score matching was performed using a caliper matching algorithm with a caliper width of 0.2 times the standard deviation of the propensity scores to ensure close matching between treated and untreated patients, thereby minimizing potential confounding effects. Statistical analyses were conducted using STATA (version 14, Data Analysis and Statistical Software) and R (version 4.4.1, R Foundation for Statistical Computing) for analyses.

# 3. Results

## 3.1. MCTD treatments

### 3.1.1. MCTD treatments at diagnosis

Three hundred and fifteen patients were included and followed up during 96 [40–156] months. Patient's main characteristics and treatments are described in Table 1, Table 2 and Fig. 1. Briefly, 277 (88 %) patients were females with a median [IQR] age at diagnosis of 35 [26–45] years. At MCTD diagnosis, 52 (16.5 %) patients were treatment-free, while 224 (71.1 %) received GC and/or HCQ. Thirty-nine (12.4 %) patients received DMARDs and/or IS mainly methotrexate (MTX) in 24 (7.6 %). Across the entire cohort, 192 (61 %) patients received HCQ, and 151 (47.9 %) patients received GC with a median dose of 20 [10–40] mg/day. At diagnosis, we found that HCQ and/or GC were more commonly prescribed to patients with arthralgia than to those without arthralgia (p < 0.01). Additionally, DMARDs and/or IS were more frequently prescribed to patients with sclerodactyly (p < 0.01), synovitis (p < 0.01), dyspnea (p < 0.05), PAH (p < 0.0001) and/or ILD (p = 0.01) with or without pulmonary fibrosis (PF) (p < 0.0001) and patients with elevated creatinine kinase (CK) (p < 0.01).

### 3.1.2. MCTD treatments during follow-up

During follow-up, only 10 (3.2 %) patients had remained treatment-free and 85 (27 %) GC-free (Table 2). A vast majority of patients (n = 271; 86 %) had received HCQ and almost half of the patients (n = 161; 51.1 %) had been treated with DMARDs and/or IS including MTX (n = 110, 34.9 %), mycophenolate mofetil (MMF) (n = 52, 16.5 %), cyclophosphamide (CYC) (n = 39, 12.4 %) and anti-B cell therapeutics (n = 39, 12.4 %). Overall, we found that patients who had musculoskeletal and/or lung involvement had more frequently received a DMARD and/or an IS during follow-up (Supplementary Table 2), especially MTX for patients with musculoskeletal involvement, and MMF and/or CYC for

<caption>**Table 2**</caption>

Disease diagnosis, last follow-up and cumulative treatments used in patients with MCTD.

<table><thead><tr><th></th><th>Disease diagnosis (n = 315)</th><th>Last follow-up (n = 315)</th><th>p-value<sup>a</sup></th><th>During follow-up (n = 315)</th><th>p-value<sup>b</sup></th></tr></thead><tbody><tr><td>No treatment<sup>c</sup></td><td>52 (16.5)</td><td>57 (18.1)</td><td>0.7</td><td>10 (3.2)</td><td>&lt;0.0001</td></tr><tr><td>No GC</td><td>164 (52.1)</td><td>177/312 (56.7)</td><td>0.23</td><td>85 (27)</td><td>&lt;0.0001</td></tr><tr><td>GC</td><td>151 (47.9)</td><td>137 (43.4)</td><td>0.30</td><td>230 (73)</td><td>&lt;0.0001</td></tr><tr><td>Dose mg/day</td><td>20 [10–40]</td><td>5 [5–10]</td><td>&lt;0.0001</td><td>NA</td><td>–</td></tr><tr><td>GC ≤ 5 mg/d</td><td>0 (0)</td><td>76 (24.1)</td><td>&lt;0.0001</td><td>NA</td><td>–</td></tr><tr><td>Hydroxychloroquine</td><td>192 (61)</td><td>189 (60)</td><td>0.87</td><td>271 (86)</td><td>&lt;0.0001</td></tr><tr><td>DMARDs</td><td>30</td><td>96</td><td>&lt;0.0001</td><td>149</td><td>&lt;0.0001</td></tr><tr><td>Methotrexate</td><td>24 (7.6)</td><td>49 (15.5)</td><td>&lt;0.01</td><td>110 (34.9)</td><td>&lt;0.0001</td></tr><tr><td>Azathioprine</td><td>4 (1.3)</td><td>16 (5.1)</td><td>&lt;0.01</td><td>37 (11.7)</td><td>&lt;0.0001</td></tr><tr><td>Mycophenolate mofetil</td><td>2 (0.6)</td><td>33 (10.4)</td><td>&lt;0.0001</td><td>52 (16.5)</td><td>&lt;0.0001</td></tr><tr><td>IS</td><td>6</td><td>20</td><td>0.005</td><td>66</td><td>&lt;0.0001</td></tr><tr><td>Cyclophosphamide</td><td>6 (1.9)</td><td>3 (0.9)</td><td>0.50</td><td>39 (12.4)</td><td>&lt;0.0001</td></tr><tr><td>Anti-B therapeutics</td><td>0 (0)</td><td>10 (3.2)</td><td>&lt;0.001</td><td>39 (12.4)</td><td>&lt;0.0001</td></tr><tr><td>Rituximab</td><td>0 (0)</td><td>7 (2.2)</td><td>&lt;0.01</td><td>36 (11.4)</td><td>&lt;0.0001</td></tr><tr><td>Belimumab</td><td>0 (0)</td><td>3 (0.9)</td><td>–</td><td>4 (1.3)</td><td>–</td></tr><tr><td>Other</td><td>1 (0.3)</td><td>13 (4.1)</td><td>–</td><td>29 (9.2)</td><td>&lt;0.0001</td></tr><tr><td>IVIg</td><td>4 (1.3)</td><td>2 (0.6)</td><td>–</td><td>18 (5.7)</td><td>&lt;0.01</td></tr></tbody></table>

Data are presented as number (percentage) or median with interquartile range. P-values were calculated using Chi-squared test or Fisher's exact test for qualitative variables and Mann Whitney's test for quantitative variables.

GC: glucocorticoids; DMARDs: disease-modifying antirheumatic drugs; IS: immunosuppressant; IVIg: intravenous immunoglobulin; MCTD: mixed connective tissue disease; n: number; NA: not available.

a Comparison between disease diagnosis and last follow-up.

b Comparison between cumulative incidence and last follow-up.

c No treatment indicate the absence of hydroxychloroquine, GC, DMARDs or immunosuppressive treatments.

patients with lung involvement (Supplementary Table 3).

### 3.1.3. MCTD treatments at last follow-up

At LFU, 57 (18.1 %) patients were treatment-free. HCQ was administered to 189 (59.8 %) patients, and GC to 137 (43.4 %) patients with 76 (24.1 %) patients with a dose ≤5 mg/day. One hundred and forty-eight (47 %) patients received GC and/or HCQ. Hundred and ten (34.9 %) patients were treated with DMARDs/IS, particularly MTX in 49 (15.6 %) patients and MMF in 33 (10.5 %) (Table 2). Thus, at LFU, patients were more frequently receiving DMARDs and/or IS than at diagnosis (n = 76, 24.6 % vs. n = 39, 12.4 %; p < 0.001).

## 3.2. Impact of MCTD treatments on prognosis

### 3.2.1. Impact of MCTD treatments on clinical remission

To further evaluate the impact of treatments on MCTD patient prognosis, we assessed clinical remission, dCTD progression, life-threatening complications (PAH and/or ILD) occurrence and death. At LFU, 137 (43.5 %) patients achieved remission. When comparing patients who achieved remission to those who did not (Supplementary Table 4), we found that patients who achieved remission were more likely to remain treated with GC and/or HCQ alone (n = 79, 57.7 % vs. n
<figure><img src="image_5.png" /><figcaption>Fig. 1. Treatment evolution in 315 MCTD patients</figcaption></figure>

Anti-B: anti-B cell therapeutics; AZA: Azathioprine, CYC: cyclophosphamide; DMARD: disease-modifying antirheumatic drugs; GC: glucocorticoids; HCQ: hydroxychloroquine; IS: immunosuppressant; MCTD: Mixed connective tissue disease; MMF: mycophenolate mofetil, MTX: methotrexate; IVIg: intravenous immunoglobulins.

= 65, 36.5%; p < 0.001) including HCQ alone (n = 40, 29.2% vs. n = 26, 14.6%; p < 0.01), than patient who did not. Along the same line, patients who did not achieve remission received more frequently a DMARD and/or an IS than other patients (n = 108, 60.7% vs. n = 53, 38.7%; p < 0.001).

### 3.2.2. Impact of MCTD treatments on the evolution towards a dCTD

During follow-up, 86 patients (27.3 %) evolved to a dCTD (MCTD-dCTD) with 49 (15.6 %) fulfilling the SSc classification criteria, 39 (12.4 %) the SLE classification criteria and 11 (3.5 %) the SjD classification criteria. When comparing MCTD-dCTD patients to patients who remained classified as MCTD (Table 3), we did not find any significant difference among treatments at disease diagnosis. During follow-up, MCTD-dCTD patients had received significantly less HCQ alone (n = 7, 8.1% vs. n = 59, 18.7%; p < 0.001), significantly more DMARDs and/or IS than MCTD patients (n = 61, 70.9% vs. n = 100, 43.7%; p < 0.0001). Along the same way, at LFU, MCTD-dCTD patients were significantly less treatment-free than MCTD patients (n = 7, 8.1% vs. n = 50, 21.8%; p = 0.005), had significantly more DMARDs and/or IS (n = 42, 48.8% vs. n = 68, 29.7%; p = 0.001), and had higher doses of GC (7.5 [5–10] mg/day vs. 5 [5–10] mg/day; p < 0.01).

### 3.2.3. Impact of MCTD treatments on life-threatening complication (i.e. ILD and PAH)

To better study the impact of treatments in ILD and/or PAH-development, we have performed analysis on MCTD patients who did not evolve toward a dCTD and who did not have a ILD and/or a PAH at disease diagnosis (n = 205; 65.1 % for ILD alone, n = 220; 69.8 % for PAH alone, and n = 201; 63.6 % for both). Among them, 24 (11.7 %) patients developed ILD, and 6 (2.9 %) patients developed PAH. We found that, at diagnosis, MCTD patients who did not develop ILD

received significantly more often HCQ combined or not with additional treatment (n = 119/181, 65.7 % vs. n = 10/24, 44%; p = 0.03) or HCQ alone (n = 71/181, 39.2 % vs. n = 4/24, 16.7%; p = 0.04) than patients who developed ILD. Along the same way, at diagnosis, MCTD patients who did not develop ILD or PAH received significantly more HCQ combined or not with additional treatment (n = 116/174, 66.7 % vs. n = 11/27, 40.7%; p < 0.01) or HCQ alone (n = 71/174, 40.8 % vs. n = 4/27, 14.8%; p = 0.01) than MCTD patients who developed these complications (Table 4). To confirm these results, we performed a sensitive analysis (Supplementary Table 5 and Supplementary Fig. 1). After matching, 152 patients were included in the analysis for ILD, 166 for PAH, and 148 for ILD and/or PAH. We confirmed that MCTD patients who did not develop ILD or PAH received significantly more HCQ, either combined with additional treatment (OR = 0.38 [0.014–0.95]) or HCQ alone (OR = 0.18 [0.28–0.66]), at disease diagnosis compared to those who developed these complications (Supplementary Table 6).

### 3.2.4. Impact of MCTD treatments on global survival

Eighteen patients (5.7 %) died after a median follow-up of 96 [40–156] months. Causes of death were PAH (n = 6), ILD (n = 2), septic shock (n = 5, including 3 on corticosteroids), cancer (n = 3), myocardial infarction (n = 1), and stroke (n = 1). When we compared the treatments received by these patients to the others, we did not find any statistical difference between the two groups at diagnosis or during follow-up (Supplementary Table 7).

### 3.2.5. Impact of glucocorticoids on cardiovascular risk and infectious diseases

The impact of GC on cardiovascular risk is depicted in Supplementary Table 8. Briefly, at the time of MCTD diagnosis, 25 (7.9 %) patients had hypertension, 9 (2.9 %) had diabetes, and 11 (3.5 %) had
<caption>**Table 3**</caption>

Comparison between patients with mixed connective tissue disease (MCTD) who evolved toward a differentiated connective tissue disease (MCTD-dCTD) and patient with stable MCTD according to treatment group at disease diagnosis, last follow-up or in cumulative incidence.

<table><thead><tr><th></th><th>All (n = 315)</th><th>MCTD (n = 229)</th><th>MCTD-dCTD (n = 86)</th><th>p-value</th><th>SSc (n = 49)</th><th>SLE (n = 38)</th><th>SjD (n = 11)</th><th>p-value<sup>a</sup></th></tr></thead><tbody><tr><td><strong>Disease diagnosis</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>No treatment<sup>b</sup></td><td>52 (16.5)</td><td>38 (16.6)</td><td>14 (16.3)</td><td>&gt;0.99</td><td>6 (12.2)</td><td>7 (18.4)</td><td>1 (9.1)</td><td>0.7</td></tr><tr><td>HCQ and/or GC</td><td>227 (72.1)</td><td>161 (70.3)</td><td>66 (76.7)</td><td>0.3</td><td>37 (75.5)</td><td>30 (78.9)</td><td>9 (81.8)</td><td>0.9</td></tr><tr><td>HCQ alone</td><td>107 (34)</td><td>81 (35.4)</td><td>26 (30.2)</td><td>0.4</td><td>13</td><td>11</td><td>6</td><td>0.2</td></tr><tr><td>GC alone</td><td>36 (11.4)</td><td>23 (10)</td><td>13 (15.1)</td><td>0.2</td><td>8</td><td>7</td><td>1</td><td>0.8</td></tr><tr><td>GC dose (mg/d)</td><td>20 [10–40]</td><td>20 [10–40]</td><td>20 [10–40]</td><td>0.86</td><td>15 [10–40]</td><td>25 [15–40]</td><td>20 [15–32.5]</td><td>0.8</td></tr><tr><td>DMARDs/IS</td><td>36 (11.4)</td><td>30 (13.1)</td><td>6 (7 %)</td><td>0.13</td><td>6 (12.2)</td><td>1 (2.6)</td><td>1 (9.1)</td><td>0.2</td></tr><tr><td>Anti-B therapeutics<sup>c</sup></td><td>0 (0)</td><td>0 (0)</td><td>0 (0)</td><td>–</td><td>0 (0)</td><td>0 (0)</td><td>0 (0)</td><td>–</td></tr><tr><td><strong>Cumulative incidence</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>No treatment<sup>b</sup></td><td>10 (3.2)</td><td>8 (3.5)</td><td>2 (2.3)</td><td>0.73</td><td>1 (2)</td><td>1 (2.6)</td><td>0 (0)</td><td>&gt;0.99</td></tr><tr><td>HCQ and/or GC</td><td>144 (45.7)</td><td>121 (52.8)</td><td>23 (26.7)</td><td>&lt;0.0001</td><td>11 (22.4)</td><td>11 (28.9)</td><td>3 (27.3)</td><td>0.8</td></tr><tr><td>HCQ alone</td><td>66 (21)</td><td>59 (18.7)</td><td>7 (8.1)</td><td>&lt;0.0001</td><td>4</td><td>1</td><td>2</td><td>0.2</td></tr><tr><td>GC alone</td><td>5 (1.6)</td><td>5 (2.2)</td><td>0 (0)</td><td>–</td><td>0</td><td>0</td><td>0</td><td>–</td></tr><tr><td>DMARDs/IS</td><td>161 (51.1)</td><td>100 (43.7)</td><td>61 (70.9)</td><td>&lt;0.0001</td><td>37 (75.5)</td><td>26 (68.4)</td><td>8 (72.7)</td><td>0.8</td></tr><tr><td>Anti-B therapeutics<sup>c</sup></td><td>39 (12.4)</td><td>19 (8.3)</td><td>20 (23.3)</td><td>0.001</td><td>11 (22.4)</td><td>10 (26.3)</td><td>3 (27.3)</td><td>0.8</td></tr><tr><td><strong>Last follow-up</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>No treatment<sup>b</sup></td><td>57 (18.1)</td><td>50 (21.8)</td><td>7 (8.1)</td><td>0.005</td><td>5 (10.2)</td><td>2 (5.3)</td><td>1 (9.1)</td><td>0.6</td></tr><tr><td>HCQ and/or GC</td><td>148 (47)</td><td>111 (48.5)</td><td>37 (43)</td><td>0.3</td><td>20 (40.8)</td><td>16 (42.1)</td><td>5 (45.5)</td><td>&gt;0.99</td></tr><tr><td>HCQ alone</td><td>96 (30.5)</td><td>75 (32.8)</td><td>21 (24.4)</td><td>0.1</td><td>9</td><td>9</td><td>3</td><td>0.7</td></tr><tr><td>GC alone</td><td>23 (7.3)</td><td>14 (6.1)</td><td>9 (10.5)</td><td>0.2</td><td>7</td><td>3</td><td>0</td><td>0.4</td></tr><tr><td>GC dose (mg/d)</td><td>5 [5–10]</td><td>5 [5–10]</td><td>7.5 [5–10]</td><td>&lt;0.01</td><td>8 [5–10]</td><td>8 [5–20]</td><td>5 [5–7.5]</td><td>0.27</td></tr><tr><td>DMARDs/IS</td><td>110 (34.9)</td><td>68 (29.7)</td><td>42 (48.8)</td><td>0.001</td><td>24 (49)</td><td>20 (52.6)</td><td>5 (45.5)</td><td>0.96</td></tr><tr><td>Anti-B therapeutics<sup>c</sup></td><td>10 (3.2)</td><td>5 (2.2)</td><td>5 (5.8)</td><td>0.16</td><td>2 (4.1)</td><td>5 (13.2)</td><td>1 (9.1)</td><td>0.3</td></tr></tbody></table>

Data are presented as number (percentage) or median with interquartile range. P-value were calculated using Chi-squared test or Fisher's exact test for qualitative variables, Mann Whitney's or Kruskal-Wallis test for quantitative variables.

dCTD: differentiated connective tissue disease; DMARDs: disease-modifying antirheumatic drugs; GC: glucocorticoids; HCQ: hydroxychloroquine; IS: immunosuppressants; MCTD: mixed connective tissue disease; MCTD-dCTD: MCTD who evolved toward a dCTD; n: number; SLE: Systemic lupus erythematosus; SjD: Sjögren's disease; SSc: systemic sclerosis.

<caption>**Table 4**</caption>

Occurrence of interstitial lung disease and/or pulmonary arterial hypertension in patients with MCTD treated with hydroxychloroquine at disease diagnosis.

<table><thead><tr><th>ILD</th><th>All (n = 205)</th><th>MCTD without ILD (n = 181)</th><th>MCTD-ILD (n = 24)</th><th>p-value</th></tr></thead><tbody><tr><td>HCQ alone<sup>a</sup></td><td>75 (36.6)</td><td>71 (39.2)</td><td>4 (16.7)</td><td>0.04</td></tr><tr><td>HCQ</td><td>129 (62.9)</td><td>119 (65.7)</td><td>10 (41.7)</td><td>0.02</td></tr><tr><td><strong>PAH</strong></td><td><strong>All (n=220)</strong></td><td><strong>MCTD without PAH (n=199)</strong></td><td><strong>MCTD-PAH (n=6)</strong></td><td></td></tr><tr><td>HCQ alone<sup>a</sup></td><td>80 (36.4)</td><td>80 (40.2)</td><td>0 (0)</td><td>0.09</td></tr><tr><td>HCQ</td><td>137 (62.3)</td><td>134 (67.3)</td><td>3 (50)</td><td>0.7</td></tr><tr><td><strong>ILD or PAH</strong></td><td><strong>All (n=201)</strong></td><td><strong>MCTD without ILD or PAH (n=174)</strong></td><td><strong>MCTD-ILD or MCTD-PAH (n=27)</strong></td><td></td></tr><tr><td>HCQ alone<sup>a</sup></td><td>75 (37.3)</td><td>71 (40.8)</td><td>4 (14.8)</td><td>0.01</td></tr><tr><td>HCQ</td><td>127 (63.2)</td><td>116 (66.7)</td><td>11 (40.7)</td><td>&lt;0.01</td></tr></tbody></table>

Data are presented as number (percentage). P-values were calculated using Chi-squared test or Fisher test.

HCQ: hydroxychloroquine; ILD: interstitial lung disease; MCTD: Mixed connective tissue disease; n = number; PAH: pulmonary arterial hypertension.

a HCQ alone indicates hydroxychloroquine without glucocorticoids, disease-modifying antirheumatic drugs, or immunosuppressive treatment.

dyslipidemia. During follow-up, GC-treated patients (N = 230) developed hypertension in 29 (12.6 %), diabetes in 9 (3.9 %), and dyslipidemia in 6 (2.6 %). In contrast, patients who did not receive GC developed these conditions less frequently. Additionally, GC-treated patients experienced myocardial infarction, stroke, or peripheral arterial disease more frequently than patients who did not receive GC, leading to death in 2 patients. As mentioned above, 3 GC-treated

patients died due to septic shock.

### 3.3. Anti-B cell treatments in MCTD

We found that a significant proportion of MCTD patients (n = 39, 12.4 %) received anti-B cell therapeutics during follow-up (Supplementary Table 9). We found that patients of Afro-Caribbean origin (n = 19/39, 48.7 % vs. 73/272, 26.8 %; p = 0.02) or patients with ILD (n = 9, 23.1 % vs. n = 28, 10.1 %; p = 0.02), received anti-B cell therapeutics significantly more often at disease diagnosis. During follow-up, patients who had received anti B-cell treatment were more likely to experience myalgia (n = 25, 64.1 % vs. n = 119, 43.1 %; p = 0.01), dyspnea (n = 24, 61.5 % vs. n = 104, 37.7 %; p = 0.005), ILD (n = 19, 48.7 % vs. n = 68, 24.6 %; p < 0.01), PF (n = 10, 25.6 % vs. n = 25, 9.1 %; p < 0.01), PAH (n = 9, 23.1 % vs. n = 15, 5.4 %; p < 0.0001), a restrictive pattern on pulmonary function tests (n = 18, 46.2 % vs. n = 44, 15.9 %; p < 0.0001) or altered diffusing capacity of the lungs for carbon monoxide (DLCO) (n = 27, 69.2 % vs. n = 112, 40.6 %; p = 0.001), and anti-SSA/Ro Abs (n = 13, 33.3 % vs. n = 53, 19.2 %; p < 0.05) than others. These findings persisted at LFU. Lastly, patients who progressed to a dCTD were also more likely to receive anti-B cell therapeutics compared to those who did not (n = 20, 51.3 % vs. n = 66, 23.9 %; p < 0.0001; OR = 3.35 [1.68–6.70]), particularly those who progressed to SSc (n = 11, 28.2 % vs. n = 38, 13.8 %; p < 0.05; OR = 2.46 [1.09–5.25]) or SLE (n = 10, 25.6 % vs. n = 28, 10.1 %; p < 0.01; OR = 3.05 [1.30–6.78]).

### 4. Discussion

To the best of our knowledge, therapeutic agents and their efficacy in MCTD have been rarely studied in the literature, with only data from a few descriptive studies that included a small number of patients without excluding patients with dCTDs [6–11]. This lack of data has been raised

<footnote>a Comparison between SSc, SLE and SjD.</footnote>

<footnote>b No treatment indicate the absence of hydroxychloroquine, glucocorticoids, DMARDs or immunosuppressant treatments.</footnote>

<footnote>c Anti-B therapeutics referred as rituximab or belimumab.</footnote>
as an important unmet need by many authors and by the European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases (ERN ReCONNET) group [12,16]. The present work represents the largest study focusing on treatments in MCTD patients with strict exclusion criteria (i.e., absence of other CTD at presentation according to current classification criteria), allowing to retrospectively analyze treatments prescribed in a homogeneous cohort of MCTD patients with a long follow-up. Importantly, the main findings of this study were that: (i) MCTD had an overall good prognosis and, thus, many patients were in remission with GC and/or HCQ, (ii) MCTD patients who had PAH and/or ILD and/or evolved toward a dCTD needed more often a treatment with DMARDs and/or IS, (iii) MCTD patients treated at diagnosis with HCQ seemed to develop PAH and/or ILD less frequently, and (iv) anti-B cell therapeutics have been used non-negligibly in MCTD patients.

Sharp and colleagues had initially reported that MCTD has a favorable prognosis and a very good response to GC alone. GC are indeed used extensively in MCTD patients (76.6 % in our study and in 80–100 % of patients in literature series [7,9,10]), but their place in the therapeutic strategy for MCTD can be debated. Indeed, it is important to note that a few patients do not require any treatment (around 3 % in previous studies [9] and ours) and that 20–25 % of patients reach clinical remission without any use of GC. In contrast, 50–75 % of patients required a treatment other than GC (HCQ, DMARDs and/or IS), highlighting that GC may not be sufficient to treat MCTD [7,9,10], and that other treatments are needed. In addition, long-term GC therapy should be minimized to avoid various side effects, including irreversible organ damage, as demonstrated in our cohort with an impact on cardiovascular and infectious disease risk, as well as mortality [31,32].

HCQ has been extensively used in our study (86 % of our patients), as in the other MCTD cohorts, with 50–80 % of patients receiving antimalarial drugs [7,10]. HCQ is proposed as a major treatment in MCTD patients [16]. In our study, HCQ and/or GC allowed a good control of MCTD disease in about half of MCTD patients (48.9 %), in agreement with other studies [7], which also reflect the overall good prognosis of the disease. Although we did not find any association between treatment with HCQ and the risk of evolving toward a dCTD, we found that MCTD patients who did not develop PAH and/or ILD more frequently received HCQ at diagnosis. However, we did not find a statistical effect on PAH, and the effect on ILD was not confirmed in the sensitivity analysis, likely due to insufficient power resulting from the reduced number of participants after propensity score matching. Previous works reported the potential benefit of HCQ to delay SLE onset in at-risk patients [33,34] but also to prevent PAH progression in SLE [35], to limit the occurrence of overlap CTD or other autoimmune diseases in SLE [36], or to prevent childhood ILD [37]. In a study of 300 SLE patients, 48 (16 %) developed ILD, and the authors found patients with SLE-associated ILD were significantly more likely to discontinue HCQ during follow-up (27.1 % vs. 15.1, p = 0.04), suggesting a protective role of HCQ in the development of ILD in SLE [38]. In a recent study, Rodolfi et al. reported that SSc-PAH patients treated with HCQ had significantly better survival compared to others [39]. Altogether, these data and ours suggest that HCQ may help to prevent the development of MCTD life-threatening complications, i.e. ILD and PAH. Nevertheless, prospective studies are needed to confirm this potential effect of HCQ.

Half of the patients in this work were treated with DMARDs and/or IS, mainly MTX, azathioprine, MMF, CYC and anti-B cell therapeutics. In our study, like in previous ones in literature, the main clinical manifestations leading to the utilization of DMARDs/IS were musculoskeletal (arthralgia, synovitis, myositis) and pulmonary (dyspnea, PAH, ILD and PF) involvement [7,9,10,12,16]. MTX is the most frequently used DMARD in MCTD case series, with 71 % of patients in the Wanzenried et al. study [10] and 34.9 % in ours, reflecting the high occurrence of musculoskeletal manifestations in MCTD patients. In our study, 70.7 % of patients with synovitis, 63.2 % with myalgia, and 84 % with proven-biopsy myositis received a DMARD, essentially MTX (in 89.2 %,

69.2 %, and 60 % of the patients treated by a DMARDs/IS for synovitis, myalgia or biopsy-proven myositis, respectively). The extensive use of MTX in MCTD can be explained by its predominant role in the treatment of other CTD. MTX is the recommended cornerstone for the treatment of RA [40,41] and is recommended in cutaneous-articular SLE patient not responding to HCQ alone [32]. The other main reason to use DMARDs and/or IS was lung involvement. This is significant since lung involvement (ILD and/or PAH) is frequent (25–50 % and 3.4–43 % for ILD and PAH, respectively, in MCTD patients) and is the primary cause of death in MCTD patients [4,7,10,30,42–49]. In our study, patients with such manifestations, received mainly MMF or CYC, which is, once again, in line with the literature [9,45,46,50]. Concerning PAH, studies have suggested that patients with MCTD-associated PAH may benefit from IS [15,29,51–53], and CYC and MMF are the most commonly used IS in MCTD-associated PAH [45]. Focusing on ILD, there is no large cohort study providing data on the outcome of immunosuppressive treatment on MCTD-associated ILD. It has been suggested that, due to the acute inflammatory process involved, MCTD-ILD could respond to GC and/or DMARDs/IS treatments, as reported in previous studies [54,55]. In our study, patients with ILD frequently received MMF, as recommended in SSc-associated ILD guidelines, possibly because it presents fewer adverse effects and therefore has better tolerance than CYC [56–58].

In this work, 39 (12.4 %) patients received anti-B cell therapeutics, mainly rituximab (RTX). RTX and, more broadly, anti-B cell therapeutics may be of interest in MCTD treatment. Anti-B cell therapeutics are used in RA for uncontrolled arthritis [40,41], in IIM for myositis [59–61], in SLE-associated nephritis [62,63], in Sjögren disease-associated symptomatic cryoglobulinemia [64] and in CTD-associated ILD [13]. Santa-cruz et al. have even proposed RTX associated with GC as a first-line treatment for MCTD-associated ILD [47]. Still, there are only a few reports about RTX use in MCTD. Wanzenried et al. reported the use of RTX in 10/28 (36 %) patients and showed that their patients had low-disease activity with a median SLEDAI-2K score of 0 [0–4] and a median EUSTAR score of 1 [0–1] [10]. Moreover, there are a few reports of adults [65–70] or juvenile [71] MCTD cases treated successfully with B-cell depletion therapy, mainly for treatment-resistant arthritis, myositis, and/or thrombocytopenia. In our work, it is noteworthy that anti-B cell therapeutics were associated with myalgia, dyspnea, PAH, ILD, PF, evolution toward a dCTD (particularly SLE and SSc), and the absence of clinical remission, which is in accordance with its use in other dCTDs. From a mechanistic point of view, strategies targeting B lymphocytes are attractive in MCTD because of the potentially pathogenic role of the Abs [72–78]. Thus, anti-U1RNP Abs could act as anti-endothelial cell Abs leading to endothelial inflammation and the up-regulation of adhesion molecules, causing endothelial cell damage and leading to proliferative vasculopathy and, thus, PAH [72,73]. Additionally, it has been shown that anti-U1RNP Abs may recognize antigens on lung endothelial cells and activate local inflammation, leading to an ILD and then to PF [72–75]. Taken together, targeting B cells in MCTD could be a promising therapeutic strategy and requires further evaluation.

Our study has some limitations. First and foremost, the data from French MCTD cohort are retrospective, which may introduce treatment allocation bias. More severe cases, and potentially those evolving into dCTD, are likely to receive more aggressive treatments (DMARDs/IS), which could confound the outcomes. Additionally, some data were unavailable, including reasons for treatment changes, additions, or treatment duration. Second, we did not evaluate the impact of treatment on ILD/PF or other organ involvement, aside from life-threatening situations, clinical remission, or death. Third, we were unable to assess treatment adherence, or adverse effects of the treatments used. Fourth, due to the absence of patient-reported outcomes in MCTD, we could not assess patients' disability or quality of life. Fifth, in the absence of a specific disease activity measurement tool for MCTD, we arbitrarily used two sets of disease activity criteria to assess patient remission for the purpose of the study, as previously proposed [4,42]. Sixth, we used
single imputation via decision trees for the propensity score rather than multiple imputation due to the relatively low proportion of missing data in our database. Finally, our study describes a wide variety of treatment regimens without standardization, which may complicate the interpretation of results. These limitations highlight the need for randomized controlled prospective studies.

## 5. Conclusion

To conclude, treatments prescribed to patients with MCTD reflect the broad spectrum of the disease. HCQ and GC are cornerstones of treatment, effectively managing disease manifestations in nearly half of MCTD patients, which confirms the good prognosis of this disease. Additionally, our findings suggest that HCQ may help prevent the development of life-threatening complications in MCTD. MCTD-dCTD patients, those with ILD and/or PAH, and patients who do not achieve remission are more likely to require DMARDs and/or IS. Among DMARDs/IS, MTX was widely used for musculoskeletal manifestations, while CYC and MMF were primarily used for patients with ILD and/or PAH. Our study also suggests a potential role for anti-B cell therapeutics in the management of MCTD.

## CRediT authorship contribution statement

**Kevin Chevalier:** Writing – original draft, Methodology, Investigation, Conceptualization. **Benjamin Thoreau:** Data curation, Conceptualization. **Marc Michel:** Writing – review & editing, Validation. **Bertrand Godeau:** Writing – review & editing, Validation. **Christian Agard:** Writing – review & editing, Visualization. **Thomas Papo:** Writing – review & editing, Visualization. **Karim Sacre:** Writing – review & editing, Visualization. **Raphaële Seror:** Writing – review & editing, Visualization, Methodology. **Xavier Mariette:** Writing – review & editing, Visualization. **Patrice Cacoub:** Writing – review & editing, Validation. **Ygal Benhamou:** Writing – review & editing, Validation. **Hervé Levesque:** Writing – review & editing, Validation. **Cécile Goujard:** Writing – review & editing, Visualization. **Olivier Lambotte:** Writing – review & editing, Validation. **Bernard Bonnotte:** Writing – review & editing, Visualization. **Maxime Samson:** Writing – review & editing, Validation. **Félix Ackermann:** Writing – review & editing, Validation. **Jean Schmidt:** Writing – review & editing, Validation. **Pierre Duhaut:** Writing – review & editing, Validation. **Kahn Jean-Emmanuel:** Writing – review & editing, Validation. **Thomas Hanslik:** Writing – review & editing, Validation. **Nathalie Costedoat-Chalumeau:** Writing – review & editing, Validation. **Benjamin Terrier:** Writing – review & editing, Validation. **Alexis Regent:** Writing – review & editing, Validation. **Bertrand Dunogue:** Writing – review & editing, Validation. **Pascal Cohen:** Writing – review & editing, Validation. **Véronique LE. Guern:** Writing – review & editing, Validation. **Eric Hachulla:** Writing – review & editing, Validation. **Benjamin Chaigne:** Writing – review & editing, Validation, Supervision, Project administration, Methodology, Investigation, Formal analysis, Conceptualization. **Luc Mouthon:** Writing – review & editing, Validation, Supervision, Project administration, Conceptualization.

## Funding sources

None.

## Declaration of competing interest

None.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.jaut.2025.103420.

## References

[1] G.C. Sharp, W.S. Irvin, E.M. Tan, R.G. Gould, H.R. Holman, Mixed connective tissue disease–an apparently distinct rheumatic disease syndrome associated with a specific antibody to an extractable nuclear antigen (ENA), Am. J. Med. 52 (1972) 148–159, https://doi.org/10.1016/0002-9343(72)90064-2.

[2] E.D. Batu, A. Günalp, S. Şahin, S. Özdel, Z. Kızıldag, A. Pac Kisaarslan, İ. Bağrul, M. Kasap Cuceoglu, A. Tanatar, H.E. Sonmez, E. Sag, S. Demir, E. Çelikel, S. Cağlayan, B. Çelikel Acar, B. Sözeri, N. Aktay Ayaz, Y. Bilginer, M.H. Poyrazoğlu, E. Ünsal, Ö. Kasapçopur, S. Özen, Pediatric mixed connective tissue disease versus other overlap syndromes: a retrospective multicenter cohort study, Rheumatol. Int. 43 (2023) 1485–1495, https://doi.org/10.1007/s00296-023-05300-x.

[3] D. Gezgin Yıldırım, E. Serdaroğlu, N. Karaçayir, Ç. Yıldız, P. Esmeray Şenol, E. Nur Sunar Yayla, M. Tanıdır, N. Belder, B. Küçüklı, S.A. Bakkaloğlu, Trigeminal neuropathy as an initial manifestation in pediatric-onset mixed connective tissue disease, Turk Arch Pediatr 58 (2023) 660–663, https://doi.org/10.5152/TurkArchPediatr.2023.23100.

[4] K. Chevalier, B. Thoreau, M. Michel, B. Godeau, C. Agard, T. Papo, K. Sacre, R. Seror, X. Mariette, P. Cacoub, Y. Benhamou, H. Levesque, C. Goujard, O. Lambotte, B. Bonnotte, M. Samson, F. Ackermann, J. Schmidt, P. Duhaut, J.-E. Kahn, T. Hanslik, N. Costedoat-Chalumeau, B. Terrier, A. Regent, B. Dunogue, P. Cohen, V.L. Guern, E. Hachulla, B. Chaigne, L. Mouthon, Clinical presentation, course, and prognosis of patients with mixed connective tissue disease: a multicenter retrospective cohort, J. Intern. Med. (2023), https://doi.org/10.1111/jim.13752.

[5] S.O. Hetlevik, B. Flato, M. Rygg, E.B. Nordal, C. Brunborg, H. Hetland, V. Lilleby, Long-term outcome in juvenile-onset mixed connective tissue disease: a nationwide Norwegian study, Ann. Rheum. Dis. 76 (2017) 159–165, https://doi.org/10.1136/annrheumdis-2016-209522.

[6] S. Abdelgalil Ali Ahmed, M.E. Adam Essa, A.F. Eldow Ahmed, E.M. Elagib, N. I. Ahmed Eltahir, H.H. Awadalla, A. Hassan, A.S.M. Khair, M.A.B. Ebad, Incidence and Clinical Pattern of Mixed Connective Tissue Disease in Sudanese Patients at Omdurman Military Hospital: Hospital-Based Study, OARRR 13 (2021) 333–341, https://doi.org/10.2147/OARRR.S335206.

[7] S. Cappelli, S. Bellando Randoone, D. Martinović, M.-M. Tamas, K. Pasalić, Y. Allanore, M. Mosca, R. Talarico, D. Opris, C.G. Kiss, A.-K. Tausche, S. Cardarelli, V. Riccieri, O. Koneva, G. Cuomo, M.O. Becker, A. Sulli, S. Guiducci, M. Radić, S. Bombardieri, M. Aringer, F. Cozzi, G. Valesini, L. Ananyeva, G. Valentini, G. Riemekasten, M. Cutolo, R. Ionescu, L. Czirják, N. Damjanov, S. Rednic, M. Matucci Cerini, “To Be or not to Be,” ten years after: evidence for mixed connective tissue disease as a distinct entity, Semin. Arthritis Rheum. 41 (2012) 589–598, https://doi.org/10.1016/j.semarthrit.2011.07.010.

[8] M.R. Alves, D.A. Isenberg, “Mixed connective tissue disease”: a condition in search of an identity, Clin. Exp. Med. 20 (2020) 159–166, https://doi.org/10.1007/s10238-020-00606-7.

[9] A. Hajas, P. Szodoray, B. Nakken, J. Gaal, E. Zöld, R. Laczik, N. Demeter, G. Nagy, Z. Szekanecz, M. Zeher, G. Szegedi, E. Bodolay, Clinical course, prognosis, and causes of death in mixed connective tissue disease, J. Rheumatol. 40 (2013) 1134–1142, https://doi.org/10.3899/jrheum.121272.

[10] A. Wanzenried, A. Garaiman, S. Jordan, O. Distler, B. Maurer, The enigma of mixed connective tissue disease—challenges in routine care, Clin. Rheumatol. 41 (2022) 3503–3511, https://doi.org/10.1007/s10067-022-06286-w.

[11] X. Shan, Y. Ge, Interstitial lung disease in patients with mixed connective tissue disease: a retrospective study, Int. J. Graph Multimed. 17 (2024) 2091–2099, https://doi.org/10.2147/JGM.S464704.

[12] B. Chaigne, C.A. Scirè, R. Talarico, T. Alexander, Z. Amoura, T. Avcin, L. Beretta, A. Doria, A. Guffroy, V. Guimarães, É. Hachulla, T. Krieg, D. Launay, G. Lepri, P. Moinzadeh, U. Müller-Ladner, S. Rednic, A. Rodrigues, S.W. Tas, R.F. Van Vollenhoven, A. Vieira, S. Bombardieri, J.E. Fonseca, I. Galetti, M. Schneider, V. Smith, M. Cutolo, M. Mosca, R. Fischer-Betz, Mixed connective tissue disease: state of the art on clinical practice guidelines, RMD Open 4 (2019) e000783, https://doi.org/10.1136/rmdopen-2018-000783.

[13] T.M. Maher, V.A. Tudor, P. Saunders, M.A. Gibbons, S.V. Fletcher, C.P. Denton, R. K. Hoyles, H. Parfrey, E.A. Renzoni, M. Kokosi, A.U. Wells, D. Ashby, M. Szigeti, P. L. Molyneaux, M. Akil, D. Babalis, N. Chaudhuri, F. Chua, A. Data, D. Desai, S. Dubey, N. Dwyer, M. Flather, R. Fordham, C. Grossi Sampedro, F. Hall, I. Jakupovic, G. Keir, B. Patel, H. Penn, A. Rajasekaran, L.G. Spencer, V. Tsipouri, Z. Wu, G. Xydopoulos, F. Zanghelinii, Rituximab versus intravenous cyclophosphamide in patients with connective tissue disease-associated interstitial lung disease in the UK (RECITAL): a double-blind, double-dummy, randomised, controlled, phase 2b trial, Lancet Respir. Med. 11 (2023) 45–54, https://doi.org/10.1016/S2213-2600(22)00359-9.

[14] E.L. Matteson, C. Kelly, J.H.W. Distler, A. Hoffmann-Vold, J.R. Seibold, S. Mittoo, P.F. Dellaripa, M. Aringer, J. Pope, O. Distler, A. James, R. Schlenker-Herceg, S. Stowasser, M. Quaresma, K.R. Flaherty, The INBUILD trial investigators, nintedanib in patients with autoimmune disease–related progressive fibrosing interstitial lung diseases: subgroup analysis of the INBUILD trial, Arthritis Rheumatol. 74 (2022) 1039–1047, https://doi.org/10.1002/art.42075.

[15] X. Jais, D. Launay, A. Yaici, J. Le Pavec, C. Tchérákian, O. Sitbon, G. Simonneau, M. Humbert, Immunosuppressive therapy in lupus- and mixed connective tissue disease-associated pulmonary arterial hypertension: a retrospective analysis of twenty-three cases, Arthritis Rheum. 58 (2008) 521–531, https://doi.org/10.1002/art.23303.

[16] R. Gunnarsson, S.O. Hetlevik, V. Lilleby, Ø. Molberg, Mixed connective tissue disease, Best Pract. Res. Clin. Rheumatol. 30 (2016) 95–111, https://doi.org/10.1016/j.berh.2016.03.002.
[17] G.C. Sharp, R. Kasukawa, Diagnostic criteria for classification of MCTD. Mixed Connective Tissue Disease and Antinuclear Antibodies, Elsevier, Amsterdam, 1987, pp. 23-32.

[18] D. Alarcon-Segovia, M. Villarreal, Classification and diagnostic criteria for mixed connective tissue disease, in: R. Kasukawa, G.C. Sharp (Eds.), Mixed Connective Tissue Disease and Anti-nuclear Antibodies, Elsevier Science Publishers B.V. (Biomedical Division), Amsterdam, 1987, pp. 33-40.

[19] M.F. Kahn, T. Appelboom, Syndrome de Sharp, in: M.F. Kahn, A.P. Peltier, O. Mayer, et al. (Eds.), Les Maladies Systémiques, Flammarion, Paris, 1991, pp. 545-556.

[20] R. Kasukawa, T. Tojo, S. Miyawaki, et al., Preliminary diagnostic criteria for classification of mixed connective tissue disease, in: R. Kasukawa, G.C. Sharp (Eds.), Mixed Connective Tissue Disease and Anti-nuclear Antibodies, Elsevier Science Publishers B. V. (Biomedical Division), Amsterdam, 1987, pp. 41-47.

[21] M. Aringer, K. Costenbader, D. Daikh, R. Brinks, M. Mosca, R. Ramsey-Goldman, J. S. Smolen, D. Wofsy, D.T. Boumpas, D.L. Kamen, D. Jayne, R. Cervera, N. Costedoat-Chalumeau, B. Diamond, D.D. Gladman, B. Hahn, F. Hiepe, S. Jacobsen, D. Khanna, K. Lerstrøm, E. Massarotti, J. McCune, G. Ruiz-Irastorza, J. Sanchez-Guerrero, M. Schneider, M. Urowitz, G. Bertsias, B.F. Hoyer, N. Leuchten, C. Tani, S.K. Tedeschi, Z. Touma, G. Schmajuk, B. Anic, F. Assan, T. M. Chan, A.E. Clarke, M.K. Crow, L. Czirják, A. Doria, W. Graninger, B. Halda-Kiss, S. Hasni, P.M. Izmirly, M. Jung, G. Kumano-vikas, M. Mariette, I. Padjen, J.M. Pego-Reigosa, J. Romero-Diaz, I. Rúa-Figueroa Fernández, D. Seror, G.H. Stummvoll, Y. Tanaka, M.G. Tektonidou, C. Vasconcelos, E.M. Vital, D.J. Wallace, S. Yavuz, P. L. Meroni, M.J. Fritzler, R. Naden, T. Dörner, S.R. Johnson, European League against Rheumatism/American College of Rheumatology classification criteria for systemic lupus erythematosus, Ann. Rheum. Dis. (2019), https://doi.org/10.1136/annrheumdis-2018-214819 (2019) [10.1136/annrheumdis-2018-214819].

[22] F. van den Hoogen, D. Khanna, J. Fransen, S.R. Johnson, M. Baron, O. Tynald, M. Matucci-Cerinic, R.P. Naden, T.A. Medsger, P.E. Carreira, G. Riemekasten, P. J. Clements, C.P. Denton, O. Distler, Y. Allanore, D.E. Furst, A. Gabrielli, M. D. Mayes, J.M. van Laar, J.R. Seibold, L. Czirják, V.D. Steen, M. Inanc, O. Kowal-Bielecka, U. Müller-Ladner, G. Valentini, D.J. Veale, M.C. Vonk, U.A. Walker, L. Chung, D.H. Collier, M.E. Csuka, B.J. Fessler, S. Guiducci, A. Herrick, V.M. Hsu, S. Jimenez, B. Kahaleh, P.A. Merkel, S. Sierakowski, R.M. Silver, R.W. Simms, J. Varga, J.E. Pope, Classification criteria for systemic sclerosis: an American College of rheumatology/European league against rheumatism collaborative initiative: ACR/EULAR classification criteria for SSc, Arthritis Rheum. 65 (2013) 2737-2747, https://doi.org/10.1002/art.38098, 2013.

[23] J. Kay, K.S. Upchurch, ACR/EULAR 2010 rheumatoid arthritis classification criteria, Rheumatology 51 (2012) vi5-vi9, https://doi.org/10.1093/rheumatology/kes279.

[24] I.E. Lundberg, A. Tjärnlund, M. Bottai, V.P. Werth, C. Pilkington, M.D. Visser, L. Alfredsson, A.A. Amato, R.J. Barohn, M.H. Liang, J.A. Singh, R. Aggarwal, S. Arnardottir, H. Chinoy, R.G. Cooper, A. Dankó, M.M. Dimachkie, B.M. Feldman, I.G.-D.L. Torre, P. Gordon, T. Hayashi, J.D. Katz, H. Kohsaka, P.A. Lachenbruch, B. A. Lang, Y. Li, C.V. Oddis, M. Olesinska, A.M. Reed, L. Combrowski-Sak, H. Sanner, A. Selva-O'Callaghan, Y.-W. Song, J. Vencovsky, S.R. Ytterberg, F.W. Miller, L. G. Rider, European League against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups, Ann. Rheum. Dis. 76 (2017) 1955-1964, https://doi.org/10.1136/annrheumdis-2017-211468, 2017.

[25] C.H. Shiboski, S.C. Shiboski, R. Seror, L.A. Criswell, M. Labetoulle, T.M. Lietman, A. Rasmussen, H. Scofield, C. Vitali, S.J. Bowman, X. Mariette, - The International Sjögren's Syndrome Criteria Working Group, A.M. Heidenreich, J. Lanfranchi, C. Vollenweider, M. Schiødt, V. Devauchelle, J.E. Gottenberg, A. Saraux, M. Pincemin, T. Dörner, A. Tzoufias, C. Baldini, S. Bombardieri, S. De Vita, K. Kitagawa, T. Sumida, H. Umehara, H. Bootsma, A.A. Kruize, T.R. Radstake, A. Vissink, R. Jonsson, M. Ramos-Casalos, E. Theander, S. Collacombe, B. Fisher, B. Kirkham, G. Larkin, F. Ng, S. Rauz, E. Akpek, J. Atkinson, A.N. Baer, S. Carsons, N. Carteron, T. Daniels, B. Fox, J. Greenspan, G. Illei, D. Nelson, A. Parke, S. Pillemer, B. Segal, K. Sivils, E.W. St Clair, D. Stone, F. Vivino, A. Wu, American College of rheumatology/European league against rheumatism classification criteria for primary Sjögren's syndrome: a consensus and data-driven methodology involving three international patient cohorts, Arthritis Rheumatol. 69 (2016) 35-45, https://doi.org/10.1002/art.39859, 2017.

[26] R.F. van Vollenhoven, G. Bertsias, A. Doria, O. Isenberg, E. Morand, M.A. Petri, B. A. Pons-Estel, A. Rahman, M.F. Ugarte-Gil, A. Voskuyl, L. Arnaud, I.N. Bruce, R. Cervera, N. Costedoat-Chalumeau, C. Gordon, F.A. Houssiain, M. Mosca, M. Schneider, M.M. Ward, G. Alarcon, M. Aringer, A.D. Askanase, S.-C. Bae, H. Bootsma, D.T. Boumpas, H. Brunner, A.E. Clarke, C. Coney, L. Czirják, T. Dörner, R. Faria, R. Fischer, R. Fritsch-Stork, M. Inanc, S. Jacobsen, D. Jayne, A. Kuhn, B. van Leeuw, M. Limper, X. Mariette, S. Navarra, M. Nikpour, M. H. Olesinska, G. Pons-Estel, J. Romero-Diaz, B. Rubio, Y. Schoenfeld, E. Bonfá, J. Smolen, Y.K.O. Teng, A. Tincani, M. Tsang-A-Sjoe, C. Vasconcelos, A. Voss, V. P. Werth, E. Zakharhova, C. Aranow, DORIS definition of remission in SLE: final recommendations from an international task force, Lupus S Med Sci 8 (2021) e000538, https://doi.org/10.1136/lupus-2021-000538, 2021.

[27] G. Valentini, M. Iudici, U.A. Walker, V.K. Jaeger, M. Baron, P. Carreira, L. Czirják, C.P. Denton, O. Distler, E. Hachulla, A.L. Herrick, O. Kowal-Bielecka, J. Pope, U. Müller-Ladner, M. Riemekasten, O. Avouac, M. Frerix, S. Jordan, T. Minier, E. Siegert, V.H. Ong, S. Vettori, Y. Allanore, The European Scleroderma Trials and Research group (EUSTAR) task force for the development of revised activity criteria for systemic sclerosis: derivation and validation of a preliminarily revised EUSTAR activity index, Ann. Rheum. Dis. 76 (2017) 270-276, https://doi.org/10.1136/annrheumdis-2016-209768.

[28] D.D. Gladman, D. Ibañez, M.B. Urowitz, Systemic lupus erythematosus disease activity index 2000, J. Rheumatol. 29 (2002) 288-291.

[29] M. Humbert, G. Kovacs, M.M. Hoeper, R. Badagliacca, R.M.F. Berger, M. Brida, J. Carlsen, A.J.S. Coats, P. Escribano-Subias, P. Ferrari, D.S. Ferreira, H. A. Ghofrani, G. Giannakoulas, D.G. Kiely, E. Mayer, G. Meszaros, B. Nagavci, K. M. Olsson, J. Pepke-Zaba, J.K. Quint, G. Rådegran, G. Simonne, O. Sitbon, T. Tonia, M. Toshner, J.L. Vachieri, A. Vonk Noordgeeraf, M. Delcloem, S. Rosenkranz, ESC/ERS Scientific Document Group, M. Schwerzmann, A.T. Dinh-Xuan, A. Bush, M. Abdelhamid, V. Aboyans, E. Arbustini, R. Asteggiano, J. A. Barberà, M. Beghetti, J. Celutkiene, M. Cikes, C. Condliffe, F. de Man, V. Falk, L. Fauchier, S. Gaine, N. Galié, W. Gin-Sing, J. Granton, E. Grünig, P.M. Hassoun, M. Hellemons, T. Jaarsma, B. Kjellström, F.A. Klok, A. Konradi, K.C. Koskinas, D. Kotecha, I. Lang, B.S. Lewis, A. Linhart, G.Y.H. Lip, M.L. Löchen, A. G. Mathioudakis, R. Mindham, S. Moledina, R. Naeije, J.C. Nielsen, H. Olschewski, I. Opitz, S.E. Petersen, E. Prescott, A. Rakisheva, A. Reis, A.D. Ristić, N. Roche, R. Rodrigues, C. Selton-Suty, R. Souza, A.J. Swift, R.M. Touzy, S. Ulrich, M. R. Wilkins, S.J. Wort, ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension, Eur. Heart J. 43 (2022) 3618-3731, https://doi.org/10.1093/eurheartj/ehac237, 2022.

[30] A. Perelas, A.V. Arrossi, K.B. Highland, Pulmonary manifestations of systemic sclerosis and mixed connective tissue disease, Clin. Chest Med. 40 (2019) 501-518, https://doi.org/10.1016/j.ccm.2019.05.001.

[31] Y. Katsumata, E. Inoue, M. Harigai, J. Cho, W. Louthrenoo, A. Hoi, V. Golder, C. S. Lau, A. Lateef, Y.-H. Chen, S.-F. Luo, Y.-J.J. Wu, L. Hamijoyo, Z. Li, S. Sockalingam, S. Navarra, L. Zamora, Y. Hao, Z. Zhang, M. Chan, S. Oon, K. Ng, J. Kikuchi, T. Takeuchi, F. Goldblatt, S. O'Neill, R. Tugnet, A.H.N. Law, S.-C. Bae, Y. Tanaka, N. Ohkubo, S. Kumar, R. Kandane-Rathnayake, M. Nikpour, E. F. Morand, Risk of flare and damage accrual after tapering glucocorticoids in modified serologically active clinically quiescent patients with systemic lupus erythematosus: a multinational observational cohort study, Ann. Rheum. Dis. 83 (2024) 998-1005, https://doi.org/10.1136/ard-2023-225369.

[32] A. Fanouriakis, M. Kostopoulou, J. Andersen, M. Aringer, R. Arnaud, S.-C. Bae, J. Boletis, I.N. Bruce, R. Cervera, A. Doria, T. Dörner, R.A. Furie, D.D. Gladman, F. A. Houssiain, L.S. Inés, D. Jayne, M. Kouloumas, L. Kovács, C.C. Mok, E.F. Morand, G. Moroni, M. Mosca, J. Mucke, C.B. Mukhtyar, G. Nagy, S. Navarra, I. Parodis, J. M. Pego-Reigosa, M. Petri, B.A. Pons-Estel, M. Schneider, J.S. Smolen, E. Svenssonsgren, Y. Tanaka, M.G. Tektonidou, Y.O. Teng, A. Tincani, E.M. Vital, R. F. Van Vollenhoven, C. Wincup, G. Bertsias, D.T. Boumpas, EULAR recommendations for the management of systemic lupus erythematosus: 2023 update, Ann. Rheum. Dis. 83 (2024) 15-29, https://doi.org/10.1136/ard-2023-224762.

[33] G.J. Pons-Estel, G.S. Alarcón, L. Hachuel, G. Boggio, D. Wojdyla, V. Pascual-Ramos, E.R. Soriano, V. Saurit, F.S. Cavalcanti, R.A. Guzman, M. Guibert-Toledano, M. J. Sauza Del Pozo, M.-C. Amigo, M. Alva, M.H. Esteva-Spinetti, B.A. Pons-Estel, GLADEL, Anti-malarials exert a protective effect when Mestizo patients are at increased risk of developing SLE renal disease: data from a Latin-American cohort, Rheumatology 51 (2012) 1293-1298, https://doi.org/10.1093/rheumatology/ker514.

[34] J.A. James, X.R. Kim-Howard, B.F. Bruner, M.K. Jonsson, M.T. McClain, M. R. Arbuckle, C. Walker, G.J. Dennis, J.T. Merrill, J.B. Harley, Hydroxychloroquine sulfate treatment is associated with later onset of systemic lupus erythematosus, Lupus 16 (2007) 401-409, https://doi.org/10.1177/0961203307078579.

[35] E. Hachulla, X. Jais, G. Cinquetti, P. Clerson, Z. Rottat, D. Launay, V. Cottin, G. Habib, G. Prevot, C. Chabanne, E. Fois, Z. Amoura, L. Mounth, V. Le Guern, D. Montani, G. Simonneau, M. Humbert, V. Sobanski, O. Sitbon, M.H. Balquet, J.-M. Ziza, J.-P. Clauvel, J.-C. Brouet, C. Pison, J.-F. Chabot, J.-F. Velly, P.-D. Dos Santos, J.-C. Meurice, A.-L. Fauchais, J. Guillevin, J. Cadran, J. Traclet, J.-F. Mornex, P. Mabo, A. Didier, Pulmonary arterial hypertension associated with systemic lupus erythematosus, Chest 153 (2018) 143-151, https://doi.org/10.1016/j.chest.2017.08.014.

[36] N. Mena-Vázquez, A. Fernández-Nebro, M. Pego-Reigosa, M. Galindo, A. Melissa-Anzola, E. Uriarte-Isacelay, A. Olivé-Marqués, E. Aurrecoechea, M. Freire, E. Tomero, M.J. García-Villanueva, C. Stoye, E. Salas-Heredia, J.A. Bernal-Vidal, E. Salgado, R. Blanco, F. Javier Novoa, M. Ibáñez-Barcelo, V. Torrente-Segarra, J. Narvaez, J. Calvet, C. Moriano Morales, T. Ramon Vazquez-Rodriguez, P. Garcia De La Peña, C. Bohórquez, J.L. Andreu-Sánchez, T. Cobo-Ibañez, G. Bonilla, N. Lozano-Rivas, C. Montilla, F.J. Toyos, J.L.M. De La Fuente, L. Expósito, M. E. Ruiz-Lucea, E. Vals, J. Manero-Ruiz, J.A. Bernal-Vidal, I. Rúa-Figueroa, Hydroxychloroquine is associated with a lower risk of polyautoimmunity: data from the RELESSER Registry, Rheumatology 59 (2020) 2043-2051, https://doi.org/10.1093/rheumatology/kez562.

[37] R. Dinwiddie, N. Sharief, O. Crawford, Idiopathic interstitial pneumonitis in children: a national survey in the United Kingdom and Ireland, Pediatr. Pulmonol. 34 (2002) 23-29, https://doi.org/10.1002/ppul.10125.

[38] N. Şenkal, E. Kiyan, A.A. Demir, Y. Yalcinkaya, A. Gul, M. Inaç, M.L. Öçal, B. Artim Esen, Interstitial lung disease in patients with systemic lupus erythematosus: a cohort study, Turk. J. Med. Sci. 52 (n.d.) 76-82. https://doi.org/10.3906/sa-g-2109-16.

[39] S. Rodolfi, C.C. Man Ng, A.M. Ruiz Bejerano, M. Kanitkar, V. Ong, C. Denton, Impact of immunosuppressive treatment on development and survival in systemic sclerosis associated pulmonary arterial hypertension (SSC-PAH), Arthritis Rheumatol. suppl 9 (2024) 76 [abstract].

[40] J.S. Smolen, R.M.B. Landewé, S.A. Bergstra, A. Kerschbaumer, A. Sepriano, D. Aletaha, R. Caporali, C.J. Edwards, K.L. Hyrich, J.E. Pope, S. De Souza, T. A. Stamm, T. Takeuchi, P. Verschueren, K.L. Winthrop, A. Balsa, J.M. Bathon, M. H. Buch, G.R. Burmester, F. Buttgereit, M.H. Cardiel, K. Chatzidionysiou,
C. Codreanu, M. Cutolo, A.A. Den Broeder, K. El Aoufy, A. Finckh, J.E. Fonseca, J.-E. Gottenberg, E.A. Haavardsholm, A. Iagnocco, K. Lauper, Z. Li, I.B. McInnes, E. F. Mysler, P. Nash, G. Poor, G.G. Ristic, F. Rivellese, A. Rubbert-Roth, H. Schulze-Koops, N. Stoilov, R. Strangfeld, A. Van Der Helm-van Mil, E. Van Duuren, T.P. M. Vliet Vlieland, R. Westhovens, D. Van Der Heijde, EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: 2022 update, Ann. Rheum. Dis. 82 (2023) 3–18, https://doi.org/10.1136/ard-2022-223356.

[41] L. Fraenkel, J.M. Bathon, B.R. England, E.W. St Clair, T. Arayssi, K. Carandang, K. D. Deane, M. Genovese, K.K. Huston, G. Kerr, J. Kremer, M.C. Nakamura, L. A. Russell, J.A. Singh, B.J. Smith, S. Venkatachalam, M.E. Weinblatt, M. Al-Gibbawi, J.F. Baker, K.E. Barbour, J.L. Barton, L. Cappelli, F. Chamseddine, M. George, S.R. Johnson, L. Kahale, B.S. Karam, A.M. Khamis, I. Navarro-Millán, R. Mirza, P. Schwab, N. Singh, M. Turgunbaev, A.S. Turner, S. Yaacoub, E.A. Akl, American College of rheumatology for the treatment of rheumatoid arthritis, Arthritis Care Res. 73 (2021) 924–939, https://doi.org/10.1002/acr.24596, 2021.

[42] S. Reiseter, R. Gunnarsson, J. Corander, J. Haydon, M.B. Lund, T.M. Aałøkken, E. Taraldsrud, S.O. Hetlevik, Ø. Molberg, Disease evolution in mixed connective tissue disease: results from a long-term nationwide prospective cohort study, Arthritis Res. Ther. 19 (2017) 284, https://doi.org/10.1186/s13075-017-1494-7.

[43] P. Ungraspr, C.S. Crowson, V.R. Chowdhary, F.C. Ernste, K.G. Moder, E. L. Matteson, Epidemiology of mixed connective tissue disease, 1985-2014; a population-based study: epidemiology of MCTD, Arthritis Care Res. 68 (2016) 1843–1848, https://doi.org/10.1002/acr.22872.

[44] F. Guimarães, M. Silvério-António, J. Martinho, A.T. Melo, D. Santos Oliveira, J. M. Pestana Lopes, A. Saraiva, L. Gago, A.M. Gomes Correia, A.L. Fernandes, S. P. Dinis, R. Nicolau, S.P. Silva, C. Costa, The Beirão, A. Furtado, P.M. Azevedo Abreu, N. Khmelinskii, C. Afonso, D. Peixoto, AB0655 clinical and immunological features of a Portuguese cohort of mixed connective tissue disease, Ann. Rheum. Dis. 81 (2022) 1454.2–1455, https://doi.org/10.1367/annrheumdis-2022-eular.617.

[45] B. Chaigne, K. Chevalier, A. Boucly, C. Agard, A. Gude, A. Baudot, B. Chabané, V. Cottin, P. Fesler, F. Goupil, P. Jego, D. Launay, H. Lévesque, A. Maurac, S. Mohamed, C. Tromeur, L. Rottat, O. Sitbon, M. Humbert, L. Mouthon, In-depth characterization of pulmonary arterial hypertension in mixed connective tissue disease: a French national multicenter study, Rheumatology (2023), https://doi.org/10.1093/rheumatology/kead055 kead055.

[46] S. Reiseter, R. Gunnarsson, T. Mogens Aałøkken, M.B. Lund, G. Mynarek, J. Corander, J. Haydon, Ø. Molberg, Progression and mortality of interstitial lung disease in mixed connective tissue disease: a long-term observational nationwide cohort study, Rheumatology 57 (2018) 255–262, https://doi.org/10.1093/rheumatology/kex077.

[47] J.C. Santacruz, M.J. Mantilla, G. Rodriguez-Salas, I. Rueda, S. Pulido, D.C. Varela, J. Londono, Interstitial lung disease in mixed connective tissue disease: an advanced search, Cureus (2023), https://doi.org/10.7759/cureus.36204.

[48] K.J. John, M. Sadiq, T. George, K. Gunasekaran, N. Francis, E. Rajadurai, T. D. Sudansarand, Clinical and immunological profile of mixed connective tissue disease and a Comparison of four diagnostic criteria, International Journal of Rheumatology 2020 (2020) 1–6, https://doi.org/10.1155/2020/9692030.

[49] R. Gunnarsson, T.M. Aałøkken, Ø. Molberg, M.B. Lund, G.K. Mynarek, Å. S. Lexberg, K. Time, A.S.S. Dhainant, L.-T. Bertelsen, Ø. Palm, K. Irgens, A. Becker-Merok, J.L. Nordeide, V. Johnsen, S. Pedersen, A. Prøven, L.S.N. Garabet, J. T. Gran, Prevalence and severity of interstitial lung disease in mixed connective tissue disease: a nationwide, cross-sectional study, Ann. Rheum. Dis. 71 (2012) 1966–1972, https://doi.org/10.1136/annrheumdis-2011-201253.

[50] F. Del Galdo, A. Lescoat, P.G. Conaghan, E. Bertoldo, J. Čolić, T. Santiago, Y. A. Suliman, M. Matucci-Cerinic, A. Gabrielli, O. Distler, A.-M. Hoffmann-Vold, I. Castellví, A. Balbir-Gurman, M. Vonk, L. Ananyeva, S. Rednic, A. Tarasova, P. Ostoijic, V. Boyadzhieva, K. El Aoufy, S. Farrington, I. Galetti, C.P. Denton, O. Kowal-Bielecka, U. Mueller-Ladner, Y. Allanore, EULAR recommendations for the treatment of systemic sclerosis: 2023 update, Ann. Rheum. Dis. (2025), https://doi.org/10.1136/ard-2024-226430. S0003496724005843.

[51] O. Distler, C. Ofner, D. Huscher, S. Jordan, S. Ulrich, G. Stähler, E. Grünig, M. Held, A. Ghofrani, M. Claussen, T.J. Lange, H. Klose, S. Rosenkranz, A. Vonk-Noordegraaf, C.D. Vizza, M. Delcroix, C. Opitz, C. Pausch, L. Scelsi, C. Neurohr, K. M. Olsson, J.G. Coghlan, M. Halank, D. Skowasch, J. Behr, K. Milger, B.A. Remppis, A. Skride, E. Jureviciene, L. Gumbiene, S. Miliauskas, J. Löffler-Ragg, H. Wilkens, D. Pittrow, M.M. Hoeper, R. Ewert, Treatment strategies and survival of patients with connective tissue disease and pulmonary arterial hypertension: a COMPERA analysis, Rheumatology 63 (2024) 1139–1146, https://doi.org/10.1093/rheumatology/kead360.

[52] O. Sanchez, O. Sitbon, X. Jaís, G. Simonneau, M. Humbert, Immunosuppressive therapy in connective tissue diseases-associated pulmonary arterial hypertension, Chest 130 (2006) 182–189, https://doi.org/10.1378/chest.130.1.182.

[53] S. Miyamichi-Yamamoto, Y. Fukumoto, K. Sugimura, T. Ishii, K. Satoh, Y. Miura, S. Tatebe, K. Nochioka, T. Aoki, Z. Do E, H. Shimokawa, Intensive immunosuppressive therapy improves pulmonary hemodynamics and long-term prognosis in patients with pulmonary arterial hypertension associated with connective tissue disease, Circ. J. 75 (2011) 2668–2674, https://doi.org/10.1253/circj-cj11-0473.

[54] B.A. Graney, A. Fischer, Advocating for early interstitial lung disease detection in mixed connective tissue disease, Rheumatology 57 (2018) 204–205, https://doi.org/10.1093/rheumatology/kex256.

[55] E. Bodolay, Z. Szekanecz, K. Dévényi, L. Galuska, I. Csípö, J. Végh, I. Garai, G. Szegedi, Evaluation of interstitial lung disease in mixed connective tissue

disease (MCTD), Rheumatology 44 (2005) 656–661, https://doi.org/10.1093/rheumatology/keh575.

[56] A.-M. Hoffmann-Vold, T.M. Maher, E.E. Philpot, A. Ashrafzadeh, R. Barake, S. Barsotti, C. Bruni, P. Carducci, P.E. Carreira, I. Castellví, F. Del Galdo, J.H. W. Distler, I. Foeldvari, P. Fraticelli, P.M. George, B. Griffiths, A. Guillén-Del-Castillo, A.M. Hamid, R. Horváth, M. Hughes, M. Kreuter, F. Moazedi-Fuerst, J. Olas, S. Paul, C. Rotondo, M. Rubio-Rivas, A. Seferian, M. Tomcík, Y. Uzunhan, U.A. Walker, E. Więsik-Szewczyk, O. Distler, The identification and management of interstitial lung disease in systemic sclerosis: evidence-based European consensus statements, The Lancet Rheumatology 2 (2020) e71–e83, https://doi.org/10.1016/S2665-9913(19)30144-4.

[57] G. Raghu, S.B. Montesi, R.M. Silver, T. Hussain, M. Macrea, D. Herman, H. Barnes, A. Adegunsoye, A. Azuma, L. Chung, G.C. Gardner, K.B. Highland, M. Hudson, R. J. Kaner, M. Kolb, M.B. Scholand, V. Steen, C.C. Thomson, E.R. Volkmann, F. M. Wigley, D. Burlill, K.A. Kemper, S.L. Knight, M. Ghazipura, Treatment of systemic sclerosis-associated interstitial lung disease: evidence-based recommendations. An official American thoracic society clinical practice guideline, Am. J. Respir. Crit. Care Med. 209 (2024) 137–152, https://doi.org/10.1164/rccm.202306-1113ST.

[58] D.P. Tashkin, M.D. Roth, P.J. Clements, D.E. Furst, D. Khanna, E.C. Kleerup, J. Goldin, E. Arriola, E.R. Volkmann, S. Kafaja, R. Silver, V. Steen, C. Strange, R. Wise, F. Wigley, M. Mayes, D.J. Riley, S. Hussain, S. Associati, V.M. Hsu, B. Patel, K. Phillips, F. Martinez, J. Golden, M.K. Connolly, J. Varga, J. Dematte, M. E. Hinchcliff, A. Fischer, J. Swigris, R. Meehan, A. Theodore, R. Simms, S. Volkov, D.E. Schraufnagel, M.B. Scholand, T. Frech, J.A. Molitur, K. Highland, C.A. Read, M.J. Fritzler, G.H.J. Kim, C.-H. Tseng, R.M. Elashoff, Mycophenolate mofetil versus oral cyclophosphamide in scleroderma-related interstitial lung disease (SLS II): a randomised controlled, double-blind, parallel group trial, Lancet Respir. Med. 4 (2016) 708–719, https://doi.org/10.1016/S2213-2600(16)30152-7.

[59] C.V. Oddis, R. Aggarwal, Treatment in myositis, Nat. Rev. Rheumatol. 14 (2018) 279–289, https://doi.org/10.1038/nrrheum.2018.42.

[60] C. Vodis, A.M. Reed, R. Aggarwal, L.G. Rider, D.P. Ascherman, M.C. Levesque, R. J. Barohn, B.M. Feldman, M.O. Harris-Love, D.C. Koontz, N. Fertig, S.S. Kelley, S. L. Pryber, F.W. Miller, H.E. Rockette, the RIM Study Group, Rituximab in the treatment of refractory adult and juvenile dermatomyositis and adult polymyositis: a randomized, placebo-phase trial, Arthritis Rheum. 65 (2013) 314–324, https://doi.org/10.1002/art.37754.

[61] J. Narváez, E. Canadillas, I. Castellví, J.J. Alegre, V. Vicens-Zygunt, G. Bermudo, P. Vidal-Montal, M. Molina Molina, J.M. Nolla, Rituximab in the treatment of progressive interstitial lung disease associated with the antisynthetase syndrome, Arthritis Res. Ther. 26 (2024) 122, https://doi.org/10.1186/s13075-024-03352-3.

[62] R. Furie, B.H. Rovin, F. Houssiam, A. Malvar, Y.K.O. Teng, G. Contreras, Z. Amoura, X. Yu, C.-C. Mok, M.B. Santiago, A. Saxena, Y. Green, B. Ji, C. Kleoudis, S. W. Burriss, C. Barnett, D.A. Roth, Two-year, randomized, controlled trial of belimumab in lupus nephritis, N. Engl. J. Med. 383 (2020) 1117–1128, https://doi.org/10.1056/NEJMoa2001180.

[63] R.A. Furie, G. Aroca, M.D. Cascino, J.P. Garg, B.H. Rovin, A. Alvarez, H. Fragoso-Loyo, E. Zuta-Santillan, T. Schindler, P. Brunetta, C.M. Looney, I. Hassan, A. Malvar, B-cell depletion with obinutuzumab for the treatment of proliferative lupus nephritis: a randomised, double-blind, placebo-controlled trial, Ann. Rheum. Dis. 81 (2022) 100–107, https://doi.org/10.1136/annrheumdis-2021-220920.

[64] K. Chevalier, R. Belkhir, R. Seror, X. Mariette, G. Nocturne, Efficacy of a sequential treatment by anti-CD 20 monoclonal antibody and belimumab in type II cryoglobulinaemia associated with primary Sjögren syndrome refractory to rituximab alone, Ann. Rheum. Dis. 79 (2020) 1257–1259, https://doi.org/10.1136/annrheumdis-2020-217481.

[65] L. Dunkley, M. Green, A. Gough, Comment on: a case of Raynaud's phenomenon in mixed connective tissue disease responding to Rituximab therapy response, Rheumatology 46 (2007) 1628–1629, https://doi.org/10.1093/rheumatology/kem208.

[66] M. Haroon, D. O'Gradaigh, D. Foley-Nolan, A case of Raynaud's phenomenon in mixed connective tissue disease responding to rituximab therapy, Rheumatology 46 (2007) 718–719, https://doi.org/10.1093/rheumatology/kem003.

[67] S.E. Rudolph, M. Kouba, P. Hrdlicka, (Severe corticoid-refractory autoimmune thrombocytopenia associated with mixed connective tissue disease (Sharp's syndrome). Treatment with rituximab), Dtsch. Med. Wochenschr. 134 (2009) 1734–1738, https://doi.org/10.1055/s-0029-1234008.

[68] P. Vela, F. Sivera, E. Batlle-Gualda, M. Mayor, A. García-Manzanares, E. Pascual, Severe ischemia following treatment with rituximab in a patient with mixed connective tissue disease: an unusual complication, Lupus 19 (2010) 1005–1006, https://doi.org/10.1177/0961203310369145.

[69] R. Gunnarsson, I.-M. Gilboe, T. Garen, Ø. Molberg, Evaluating the therapeutic effects of B cell depletion therapy with rituximab in a longitudinal cohort of mixed connective tissue disease patients, ACR Meeting Abstracts (2012) S1–S1216.

[70] M. Pascual, J. Narváez, G. Albert Espi, M. López de Recalde, A. Zacarias, J. J. Alegre, Rituximab in refractory mixed connective tissue disease: an observational study [abstract], Arthritis Rheumatol. 67 (suppl 10) (2015). https://acrabstracts.org/abstract/rituximab-in-refractory-mixed-connective-tissue-disease-ase-an-observational-study/.

[71] A.F. Jansson, C. Sengler, J. Kuemmerle-Deschner, B. Gruhn, A.B. Kranz, J. Lehmann, D. Kleinert, L. Pape, H.J. Girschick, I. Foeldvari, D. Haffner, J.P. Haas, D. Moebius, D. Foell, J. Peitz, V. Grote, B cell depletion for autoimmune diseases in paediatric patients, Clin. Rheumatol. 30 (2011) 87–97, https://doi.org/10.1007/s10067-010-1630-0.

[72] M. Okawa-Takatsuji, S. Aotsuka, M. Fujinami, S. Uwatoko, M. Kinoshita, M. Sumiya, Up-regulation of intercellular adhesion molecule-1 (ICAM-1),
endothelial leucocyte adhesion molecule-1 (ELAM-1) and class II MHC molecules
on pulmonary artery endothelial cells by antibodies against U1-ribonucleoprotein,
Clin. Exp. Immunol. 116 (2001) 174-180, https://doi.org/10.1046/j.1365-
2249.1999.00864.x.

[73] M. Okawa-Takatsuji, S. Aotsuka, S. Uwatoko, M. Takaono, K. Iwasaki, M. Kinoshita, M. Sumiya, Endothelial cell-binding activity of anti-U1-ribonucleoprotein antibodies in patients with connective tissue diseases, Clin. Exp. Immunol. 126 (2008) 345-354, https://doi.org/10.1046/j.1365-2249.2001.01669.x.

[74] E.L. Greidinger, M.F. Foecking, J. Magee, L. Wilson, S. Ranatunga, R.A. Ortmann, R.W. Hoffman, A major B cell epitope present on the apoptotic but not the intact form of the U1-70-kDa ribonucleoprotein autoantigen, J. Immunol. 172 (2004) 709-716, https://doi.org/10.4049/jimmunol.172.1.709.

[75] M.P. Keith, C. Moratz, G.C. Tsokos, Anti-RNP immunity: implications for tissue injury and the pathogenesis of connective tissue disease, Autoimmun. Rev. 6 (2007) 232-236, https://doi.org/10.1016/j.autrev.2006.08.007.

[76] E.L. Greidinger, M.F. Foecking, K.R. Schäfermeyer, C.W. Bailey, S.L. Primm, D. R. Lee, R.W. Hoffman, T cell immunity in connective tissue disease patients targets the RNA binding domain of the U1-70kDa small nuclear ribonucleoprotein, J. Immunol. 169 (2002) 3429-3437, https://doi.org/10.4049/jimmunol.169.6.3429.

[77] E.L. Greidinger, R.W. Hoffman, Autoantibodies in the pathogenesis of mixed connective tissue disease, Rheum. Dis. Clin. N. Am. 31 (2005) 437-450, https://doi.org/10.1016/j.rdc.2005.04.004.

[78] M.-M. Holyst, D.L. Hill, S.O. Hoch, R.W. Hoffman, Analysis of human t cell and b cell responses against u small nuclear ribonucleoprotein 70-kd, b, and d polypeptides among patients with systemic lupus erythematosus and mixed connective tissue disease, Arthritis Rheum. 40 (1997) 1493-1503, https://doi.org/10.1002/art.1780400818.