Anti-SS-A-ab for PM/DM relapse

Original Article
Anti-SS-A/Ro antibody positivity as a risk factor for relapse in patients withpolymyositis/dermatomyositis

Noriko Toyota-Tatebe, Ken-Ei Sada, Yosuke Asano, Sonia Zeggar, Sumie Hiramatsu, Yoshia Miyawaki, Keiji
Ohashi, Michiko Morishita, Takayuki Katsuyama, Eri Katsuyama, Haruki Watanabe, Mariko Takano-Narazaki,
Katsue Sunahori-Watanabe, Tomoko Kawabata, and Jun Wada

Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate
School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama, 700-8558,
Japan.

Text pages:10, tables:2, figures:2

Key words: anti-SS-A/Ro antibodies, dermatomyositis, polymyositis, ,Correspondence to: Ken-Ei Sada, MD, PhD, Department of Nephrology, Rheumatology, Endocrinology andMetabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences,2-5-1 Shikata-cho, Kitaku, Okayama City, 700-8558, Japan.
Tel: +81-86-235-7235. Fax: +81-86-222-5214. E-mail: sadakenn@md.okayama-u.ac.jp1Anti-SS-A-ab for PM/DM relapse
ABSTRACT
Objective: To elucidate predictors of relapse in patients with polymyositis and dermatomyositis (PM/DM).
Methods: Fifty PM/DM patients who achieved disease stabilization at Okayama University Hospital in
2004-2014 were enrolled retrospectively. Candidate predictors such as demographic factors, clinicalsymptoms, laboratory data, and treatment status were compared.
Results: The mean age of enrolled patients was 58 years; 34 were female. The patient groupings were as
follows: 21 with PM, 27 with DM, and 2 with clinically amyopathic DM. During a mean observation periodof 685 days, 5 patients (10%) died and 20 (40%) relapsed. The relapsed patients displayed baseline muscle
weakness less frequently (85% vs. 100%, p = 0.03) and anti-SS-A/Ro antibody more frequently (65% vs.
27%, p = 0.007). Anti-SS-A/Ro-positive patients exhibited a higher relapse rate than anti-SS-A/Ro-negative
patients (log-rank test, p = 0.03). Anti-SS-A/Ro-positive patients also exhibited higher anti-Jo-1 antibody
positivity and lower levels of serum complement. After adjusting anti-Jo-1 antibody positivity, age, sex, CK <500 IU/L, and lung involvement, anti-SS-A/Ro positivity was still an independent risk factor for higher
relapse-rate (odds ratio, 5.5; 95% confidence interval, 1.4-25.1).
Conclusion: Anti-SS-A/Ro antibody positivity may be a useful biomarker for prediction of relapse.

2Anti-SS-A-ab for PM/DM relapse
INTRODUCTION
Polymyositis (PM) and dermatomyositis (DM) are idiopathic inflammatory diseases characterized byproximal skeletal muscle weakness and/or distinctive skin manifestations. Various vital organs such as thelung and heart are involved; malignancies may develop. Clinical symptoms are temporarily improved inmany patients on treatments, but most experience relapse and/or chronic progression [1-3].
Several reports have investigated risk factors for mortality in patients with PM/DM, such as malignancy,
male sex, advanced age, and lung involvement, but the risk factors for relapse remain unexplored [1-6].
Recently, clinically amyopathic DM (CADM), which exhibits the characteristic skin lesions of DM but lacks
muscle weakness, was also reported as a mortality risk, but the correlation between CADM and relapse is still
unknown [5, 6].
Anti-SS-A/Ro is one of the autoantibodies associated with inflammatory myopathies. Previous reports
have shown that patients with inflammatory myopathies are sometimes positive for anti-SS-A/Ro-52
antibody [7-10] and other reports have shown that anti-SS-A/Ro positivity is a poor prognostic factor inpatients with PM/DM [4, 11]. Anti-SS-A/Ro-52 antibody is also associated with complication andprogression of interstitial lung disease (ILD) in PM/DM [12]; therefore, anti-SS-A/Ro may be associated withnot only mortality, but also with relapse in patients with PM/DM.
In the present study, we evaluated relapse in patients with PM/DM and explored the risk factors for lower
relapse after disease stabilization. We also investigated the clinical characteristics of patients with PM/DM
displaying anti-SS-A/Ro antibody positivity.

MATERIALS AND METHODSPatient selection
We conducted a retrospective study of patients with PM/DM who achieved disease stabilization during
treatment at Okayama University Hospital from 2004 to 2014. Initially, 144 patients were identified
according to the International Classification of Diseases, 9th Revision (ICD-9) codes for DM (710.3) and PM(710.4). Of these 144 patients, 33 were excluded because they were first diagnosed before 2004. Of 111
newly diagnosed patients, we enrolled 49 patients as DM / PM using the Bohan and Peter criteria (probableor definite) [13]. Subsequently, 2 of remaining 62 patients were enrolled as CADM using criteria for CADM
(i.e., showed typical cutaneous symptom of DM without clinical muscle symptoms [14]). Disease activity
was assessed based on the definition options of the myositis intention to treat activity index (MITAX) scoring3

Anti-SS-A-ab for PM/DM relapse
system [15]). Disease stabilization was defined as option ≤ 2 in all MITAX items: no exacerbation of clinicalsymptoms and muscle enzyme laboratory data for at least 4 weeks after initiation of treatment. In the end, onepatient who did not achieve disease stabilization was also excluded. Finally, 50 patients were included in thepresent study (Figure 1).
This study was conducted according to the Declaration of Helsinki and the ethical guidelines for
epidemiological research in Japan. Informed consent to participate in the study was obtained from allparticipants.
Data collection
The following data were collected at baseline: age, sex, time to diagnosis, underlying comorbidities, clinicalsymptoms, laboratory data, histological data, and treatment status. Laboratory data before the initial
treatments included creatine kinase (CK), C-reactive protein (CRP), ferritin, sialylated carbohydrate antigen(KL-6), anti-SS-A/Ro antibody (UniCAP EliA/Phadia or MESACUP-2/MBL), and anti-Jo-1 antibody
UniCAP EliA/Phadia or MESACUP-2/MBL). In 29 patients, we also measured the levels of anti-PL-7
antibody, anti-PL-12 antibody, anti-EJ antibody, anti-SRP antibody, anti-Ku antibody, anti-OJ antibody,anti-Mi-2 antibody, anti-PM-Scl75 antibody, and anti-PM-Scl100 antibody using the line blot test kit(Myositis Profile Euro line Blot test kit, Euro Immune, Lubeck, Germany). Electromyography, muscle biopsy,
and skin biopsy results were also collected. ILD was diagnosed using thoracic computed tomography.
Treatment status included an initial daily dose of glucocorticoid, and concomitant use of glucocorticoid pulse
therapy, immunosuppressants, and intravenous immunoglobulin (IVIG).
Relapse rate was the primary outcome of the present study. Relapse was defined as option ≥ 3 in at least
one MITAX item, e.g., exacerbation of muscle weakness, ILD, skin rash, arthritis, and/or elevation of
myogenic enzymes, that required additional treatment or change of treatment.
Statistical analysis
Clinical characteristics were presented as the mean ± standard deviation (SD) of the number of patients.
Continuous variables were compared using Student’s t-test or the Mann-Whitney U test depending on data
distribution, and categorical variables were compared using Fisher’s direct probability test. The association ofcandidate predictors with relapse was modeled with multivariate logistic regression analysis. Selection ofcandidate predictors was based on the result of univariate analysis and previous reports. Cumulative relapse
rate was analyzed using the Kaplan-Meier method and the log-rank test. A p-value of < 0.05 was consideredsigniﬁcant. All statistical analyses were performed using the JMP 8.0.2 software package (SAS Institute Inc.,

4

Anti-SS-A-ab for PM/DM relapse
Cary, NC, USA).

RESULTS
Baseline characteristics and treatment status
The mean age of enrolled patients was 58 years; 34 (68%) were female. The patients were classified as 21(42%) with PM (12 probable and 9 definite), 27 (54%) with DM (15 probable and 12 definite), and 2 (4%)
with CADM. Malignancy was present in 6 patients and Sjögren's syndrome was present in 3. ILD was
diagnosed in 30 (60%) patients. Proximal muscle weakness evaluated by the attending physician was foundin 47 (94%) patients and myogenic enzymes were elevated in 49 patients (98%). Antibody positivity in theenrolled patients was as follows: anti-Jo-1 antibody, 8 of 50 (16%); anti-SS-A/Ro antibody, 21 of 50 (42%);anti-PL-7 antibody, 4 of 28 (14%); anti-PL-12 antibody, 2 of 28 (7%); anti-EJ antibody, 2 of 28 (7%);
anti-SRP antibody, 2 of 28 (7%); and anti-Ku antibody, 2 of 28 (7%). Electromyography was obtained for 34
patients and 21 (62%) showed myogenic abnormalities. Muscle biopsy was performed in 38 patients and skinbiopsy was performed in 27. Histological findings were consistent with myositis in 23 (61%) of 38 patients
who underwent muscle biopsy, and were compatible with DM in 23 (85%) of 27 patients who underwent skinbiopsy.
All patients were treated with glucocorticoids as induction therapy. The mean initial prednisolone (PSL)
dose was 46 mg and concomitant glucocorticoid pulse therapy was used in 13 (26%) patients.
Immunosuppressants were used in 24 (48%) patients (tacrolimus in 12, azathioprine in 4, cyclosporine in 4,
cyclophosphamide in 3, and methotrexate in 1). IVIG was administered in 4 patients.
Clinical course and risk factors for relapse
Disease stabilization in the 50 enrolled patients was achieved at a mean of 33 days after the initiation oftreatment. After disease stabilization, 5 patients died during the mean observation period of 680 ± 697 days.
The cause of death in these 5 patients was as follows: 2 due to malignancy (one with Stage IIIA ovariancancer and the other with Stage IV lung cancer), 1 due to Pneumocystis jiroveci pneumonia (PCP), and 2 due
to unknown causes.
Twenty (40%) patients experienced relapse at least once and required additional treatments or change oftreatment. The mean period to first relapse after disease stabilization was 342 ± 317 days. All patients
experienced relapse after more than 30 days after disease stabilization. Among 20 relapsed patients, 12
showed exacerbation of myositis, 7 showed exacerbation of ILD, 4 showed exacerbation of skin lesions, and5

Anti-SS-A-ab for PM/DM relapse
2 showed exacerbation of arthritis. One patients relapsed at day 166 and died of lung cancer at day 757. The
mean daily dose of PSL was 11 ± 10 mg in 19 of 20 patients and 9 of these 20 were administered thefollowing immunosuppressants concomitantly: cyclosporine in 4 patients, tacrolimus in 2, azathioprine in 1,
and methotrexate in 2.
By univariate analysis, patients with relapse manifested baseline muscle weakness less frequently andanti-SS-A/Ro antibody more frequently than did those without relapse (85% vs. 100%, p = 0.03 and 65% vs.
27%, p = 0.007, respectively). No significant difference was observed for any other factors such as
demographic factors, complications, positivity of autoantibodies other than anti-SS-A/Ro antibody, andtreatment status (Table 1). Of 29 patients evaluated by the line blot test, patients with anti-ARS antibody
exhibited higher relapse rate than in those without anti-ARS antibody (71% vs. 25%, p = 0.01). The timefrom onset of symptoms to diagnosis tended to be longer in relapsed patients than in non-relapsed patients,
but the difference was not significant. (176 ± 182 days vs. 128 ± 135, p = 0.30). On using the log-rank test,
patients with anti-SS-A/Ro antibody also exhibited a higher relapse rate than those without anti-SS-A/Ro
antibody (p = 0.03) (Fig.2).
Differences in clinical features between anti-SS-A/Ro antibody-positive and -negative patients with
PM/DM
The characteristics of anti-SS-A/Ro antibody-positive and -negative patients with PM/DM are shown in Table
2. Age, sex, and clinical symptoms related to PM/DM, such as muscle weakness and interstitial lung disease,were comparable in both groups. Anti-Jo-1 antibody positivity was significantly more common inanti-SS-A/Ro antibody-positive patients than in -negative patients (29% vs. 7%, p = 0.04). As a wholeanti-ARS antibody, positivity was higher in anti-SS-A/Ro antibody-positive patients than in -negative
patients (79% vs. 21%, p = 0.001). As for serum complement levels were also significantly lower inanti-SS-A/Ro antibody-positive patients than in -negative patients (C3: 94 ± 21 vs. 108 ± 23, p = 0.03; C4: 20± 8 vs. 28 ± 9, p = 0.0017; and CH50: 42 ± 11 vs. 49 ± 10, p = 0.015).
After adjusting anti-Jo-1 antibody positivity in addition to age, sex, CK < 500 IU/L, and lunginvolvement, anti-SS-A/Ro antibody was still an independent risk factor for higer relapse rate (odds ratio,
5.5; 95% CI, 1.4 - 25.1).

DISCUSSION
This is the first report to demonstrate anti-SS-A/Ro antibody positivity as a risk factor for relapse in patients6

Anti-SS-A-ab for PM/DM relapse
with PM/DM. All but 1 patient achieved disease stabilization in our selected population. Of these, 5 of 50
with PM/DM died and 40% experienced relapse within the observation period.
Of 5 patients who died in the present study, 2 died due to malignancy and 1 died due to PCP, but none
died of PM/DM. Previous studies with longer observation periods (ranging from 3 to 12 years) showed thatmalignancy, male sex, advanced age, and lung involvement including ILD were possible risk factors for
mortality in patients with PM/DM [1, 3-5]. The most common cause of death in the previous studies wasmalignancy, and 2 patients died of malignancies shortly after diagnosis in our case series [1, 2, 4]. Therefore,
malignancy would be an adverse prognostic factor regardless of observation period. Advanced age, male sex,
and lung involvement are also well-known risk factors for infection in patients with connective tissue disease.
[16-18]. Since a recent report showed that infection is the leading cause of mortality among hospitalized
patients with PM/DM [19] and 1 patient also died of PCP in our study, these factors were surrogates for therisk of infectious complications.
Twenty (40%) patients experienced relapse within the observational period. Relapse rates were lower thanin previous studies (58%-65%) because of the short observation period [2]. Even though only one report
showed that advanced age, longer time to diagnosis, and ILD were possible risk factors for relapse in PM/DM
without statistical significance, these factors were not different between patients with or without relapse in
the present study [2]. Although the definition of activity of PM/DM in clinical studies was not establisheduntil recently, 65-98% of patients with PM/DM achieved improvement of clinical symptoms or laboratory
findings [1-3]. These results including our present study demonstrated that the current standard remission
induction treatment achieved substantive clinical improvement in patients with PM/DM. Considering that theinitial treatment response in PM/DM was fair, disease-related mortality risk factors may also be considered
possible factors for relapse. A previous report described ILD with mild elevation of serum CK levels inpatients with DM, indicating that CADM is a mortality risk factor [5]. As all patients without muscle
weakness, including 2 patients with CADM, experienced relapse in the present study, CADM may be a risk
factor for relapse.
Anti-SS-A/Ro is an autoantibody known to be related to inflammatory myopathies; a previous report
showed that about 20-40% of patients with inflammatory myopathies were positive for anti-SS-A/Ro-52
antibody [7-10]. Anti-SS-A/Ro-52 antibody was associated with complication and progression of ILD in
PM/DM and other connective tissue diseases [12]. Over 70% of Jo-1-positive patients with myositis exhibited
anti-SS-A/Ro-52 antibody positivity related to symptomatic ILD, malignant complication, and poor survival

7

Anti-SS-A-ab for PM/DM relapse[11]. A recent report showed that anti-SS-A/Ro antibody positivity was a poor prognostic factor not only in
Jo-1-positive populations but also in all myositis populations [4]. Even in our study, anti-Jo-1 antibody
positivity and the complication of ILD were more common in patients with anti-SS-A/Ro antibody than inthose without anti-SS-A/Ro antibody. In the present study, anti-SS-A/Ro antibody positivity was identified asa risk factor for relapse after adjusting for the complication of ILD and anti-Jo-1 antibody positivity.
Therefore, anti-SS-A/Ro antibody may also emerge as a poor prognostic factor if this study is performed witha longer observation period. In addition, lower levels of serum complement were found in anti-SS-A/Ro
antibody-positive patients, suggesting that anti-SS-A/Ro antibody may affect the pathology caused byimmune complexes in patients with PM/DM.
Several limitations warrant attention in the present study. First, we excluded a patient who did not achievedisease stabilization and therefore our treatment may be inadequate for prevention of relapse. As only one
patient did not achieve disease stabilization, the influence of selection bias was minimal. Second, our results
may be affected by indication bias because the treatments were determined at the discretion of the attending
physicians. Third, we could not assess disease activity using a validated tool such as the Disease Activity
Core Set Measures recommended by the International Myositis Assessment & Clinical Studies Groupbecause of the lack of Visual Analog Scale and Health Assessment Questionnaire data. Fourth, we could not
adjusted whole anti-ARS antibody positivity by multivariate analysis because anti-ARS antibody except for
anti-Jo-1 antibody was checked in only a half of enrolled patients. A prospective study with strict treatment
and assessment protocols should be performed to overcome these biases.
In conclusion, anti-SS-A/Ro antibody positivity was a risk factor for relapse in patients with PM/DM whoachieved disease stabilization. Anti-SS-A/Ro antibody positivity might thus be a useful biomarker forprediction of relapse after disease stabilization in patients with PM/DM.

ACKNOWLEDGEMENTS
The authors thank all medical staff members in our department.

CONFLICT OF INTEREST
Jun Wada receives speaker honoraria from Astellas, Boehringer Ingelheim, Novartis, and Tanabe Mitsubishi,
and receives grant support from Astellas, Bayer, Chugai, Daiichi Sankyo, Kissei, Kyowa Hakko Kirin, MSD,

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Anti-SS-A-ab for PM/DM relapse
Otsuka, Teijin, Torii, Pfizer, Takeda, and Taisho Toyama. None of the other authors have any conflicts ofinterest.

REFERENCES
1. Marie I, Hachulla E, Hatron PY, Hellot MF, Levesque H, Devulder B, et al. Polymyositis anddermatomyositis: short term and longterm outcome, and predictive factors of prognosis. J Rheumatol.
2001;28:2230-7.
2. Agarwal SK, Monach PA, Docken WP, Coblyn JS. Characterization of relapses in adult idiopathic
inflammatory myopathies. Clin Rheumatol. 2006;25:476-81.
3. Taborda AL, Azevedo P, Isenberg DA. Retrospective analysis of the outcome of patients with idiopathic
inflammatory myopathy: a long-term follow-up study. Clin Exp Rheumatol. 2014;32:188-93.
4. Dobloug GC, Garen T, Brunborg C, Gran JT, Molberg O. Survival and cancer risk in an unselected andcomplete Norwegian idiopathic inflammatory myopathy cohort. Seminars in arthritis and rheumatism.
2015;45:301-8.
5. Yamasaki Y, Yamada H, Ohkubo M, Yamasaki M, Azuma K, Ogawa H, et al. Longterm survival andassociated risk factors in patients with adult-onset idiopathic inflammatory myopathies and amyopathic
dermatomyositis: experience in a single institute in Japan. J Rheumatol. 2011;38:1636-43.
6. Fujisawa T, Hozumi H, Kono M, Enomoto N, Hashimoto D, Nakamura Y, et al. Prognostic factors formyositis-associated interstitial lung disease. PLoS One. 2014;9:e98824.
7. Rutjes SA, Vree Egberts WT, Jongen P, Van Den Hoogen F, Pruijn GJ, Van Venrooij WJ. Anti-Ro52
antibodies frequently co-occur with anti-Jo-1 antibodies in sera from patients with idiopathic inflammatory
myopathy. Clin Exp Immunol. 1997;109:32-40.
8. Brouwer R, Hengstman GJ, Vree Egberts W, Ehrfeld H, Bozic B, Ghirardello A, et al. Autoantibody
profiles in the sera of European patients with myositis. Ann Rheum Dis. 2001;60:116-23.
9. Koenig M, Fritzler MJ, Targoff IN, Troyanov Y, Senecal JL. Heterogeneity of autoantibodies in 100
patients with autoimmune myositis: insights into clinical features and outcomes. Arthritis Res Ther.
2007;9:R78.
10. Rozman B, Bozic B, Kos-Golja M, Plesivcnik-Novljan M, Kveder T. Immunoserological aspects of
idiopathic inflammatory muscle disease. Wiener klinische Wochenschrift. 2000;112:722-7.
11. Marie I, Hatron PY, Dominique S, Cherin P, Mouthon L, Menard JF, et al. Short-term and long-term

9Anti-SS-A-ab for PM/DM relapse
outcome of anti-Jo1-positive patients with anti-Ro52 antibody. Seminars in arthritis and rheumatism.
2012;41:890-9.
12. Ghillani P, Andre C, Toly C, Rouquette AM, Bengoufa D, Nicaise P, et al. Clinical significance ofanti-Ro52 (TRIM21) antibodies non-associated with anti-SSA 60kDa antibodies: results of a multicentric
study. Autoimmun Rev. 2011;10:509-13.
13. Bohan A, Peter JB. Polymyositis and dermatomyositis (first of two parts). N Engl J Med. 1975 Feb
13;292(7):344-7.
14. Gerami P1, Schope JM, McDonald L, Walling HW, Sontheimer RD. A systematic review of adult-onset
clinically amyopathic dermatomyositis (dermatomyositis siné myositis): a missing link within the spectrumof the idiopathic inflammatory myopathies. J Am Acad Dermatol. 2006 Apr;54(4):597-613.
15. Isenberg DA, Allen E, Farewell V, Ehrenstein MR, Hanna MG, Lundberg IE, et al, for the International
Myositis Outcome Assessment and Clinical Studies Group (IMACS). International consensus outcome
measures for patients with idiopathic inflammatory
myopathies: development and initial validation of myositis activity and damage indices in patients with adultonset disease. Rheumatology (Oxford) 2004;43:49–54.
16. Yamazaki H, Sakai R, Koike R, Miyazaki Y, Tanaka M, Nanki T, et al. Assessment of risks of pulmonary
infection during 12 months following immunosuppressive treatment for active connective tissue diseases: alarge-scale prospective cohort study. J Rheumatol. 2015;42:614-22.
17. Ruiz-Irastorza G, Olivares N, Ruiz-Arruza I, Martinez-Berriotxoa A, Egurbide MV, Aguirre C. Predictorsof major infections in systemic lupus erythematosus. Arthritis Res Ther. 2009;11:R109.
18. Feldman CH, Hiraki LT, Winkelmayer WC, Marty FM, Franklin JM, Kim SC, et al. Serious infections
among adult Medicaid beneficiaries with systemic lupus erythematosus and lupus nephritis. Arthritis &rheumatology. 2015;67:1577-85.
19. Murray SG, Schmajuk G, Trupin L, Lawson E, Cascino M, Barton J, et al. A population-based study of
infection-related hospital mortality in patients with dermatomyositis/polymyositis. Arthritis Care Res(Hoboken). 2015;67:673-80.

10Anti-SS-A-ab for PM/DM relapse
Table 1. Baseline characteristics of patients with or without relapse
With relapse

Without relapse(n=20)(n=30)

Age (years), mean (SD)54 (14)61 (12)0.08

Time to diagnosis (day), mean (SD)

176 (182)

128 (135)

0.30

Female sex, n (%)

14 (70)20 (67)0.80

PM, n (%)

6 (30)

15 (50)0.11

DM, n (%)

12 (60)15 (50)CADM, n (%)

2 (10)0 (0)Malignancy, n (%)

1 (5)

5(16)

0.21

Muscle weakness, n (%)

17 (85)30 (100)

0.03*

Interstitial lung disease, n (%)

12 (60)18 (60)1.00

CK (IU/l), mean (SD)

1636 (1881)

3506 (4791)

0.10

CRP (mg/dl), mean (SD)

1.8 (3.1)

1.2 (2.3)

0.42

Ferritin (ng/ml), mean (SD)

701 (1097)

353 (322)

0.12

KL-6 (U/ml), mean (SD)

461 (246)

481 (379)

0.84

Anti-Jo-1 antibody, n (%)

5 (25)

3 (10)

0.16

Anti-SS-A/Ro antibody, n (%)

13 (65)8 (27)

0.007*

Initial daily dose of PSL (mg/day), mean (SD)45 (12)47 (14)0.71

mPSL pulse use, n (%)

5 (25)

8 (27)

0.90

Concomitant immunosuppressant, n (%)

10 (50)14 (47)0.82

Tacrolimus, n3

9Azathioprine, n

31

Cyclosporine, n

1

3

Cyclophosphamide , n

30Methotrexate, n

0

1

1 (5)

3 (10)

p

Classification of myositis

IVIG, n (%)

11

0.52

Anti-SS-A-ab for PM/DM relapse
PM: polymyositis, DM: dermatomyositis, CADM: clinically amyopathic dermatomyositis, CK: creatine
kinase, CRP: C-reactive protein, KL-6: sialylated carbohydrate antigen, PSL: prednisolone, mPSL:
methylprednisolone, IVIG: intravenous immunoglobulin

12Anti-SS-A-ab for PM/DM relapse
Table 2. Comparison of anti-SS-A/Ro antibody-positive and -negative patients
SS-A/Ro (+)

SS-A/Ro (-)(n=21)(n=29)

Age (year), mean (SD)56 (15)60 (12)0.32

Time to diagnosis (day), mean (SD)172 (182)

129 (134)

0.33

Female sex, n (%)

17 (81)17 (59)0.95

PM

7 (33)

14 (48)

0.57

DM

13 (62)14 (48)

CADM

1 (5)

1(4)

Malignancy, n(%)

2 (10)

4 (14)

0.65

Muscle weakness

19 (91)28 (97)0.37

Interstitial lung disease, n (%)

15 (71)15 (52)0.16

CK (IU/l), mean (SD)2057 (1985)

3266 (4922)

0.29

CRP (mg/dl), mean (SD)

1.6 (3.0)

1.3 (2.3)

0.70

Ferritin (ng/ml), mean (SD)

464 (628)490 (778)

0.91KL-6 (U/ml), mean (SD)504 (284)

448 (361)

0.58

Anti-Jo-1 antibody, n (%)

6 (29)2 (7)0.039*IgG (mg/dl), mean (SD)1814 (609)1530 (670)

0.15

CH50 (U/ml), mean (SD)42 (11)49 (10)0.015*

C3 (mg/dl), mean (SD)94 (21)108 (23)

0.031*

C4 (mg/dl), mean (SD)20 (8)

28 (9)

0.0017*p

Classification of myositis, n (%)

PM: polymyositis, DM: dermatomyositis, CADM: clinically amyopathic dermatomyositis, CK: creatine
kinase, CRP: C-reactive protein, KL-6: sialylated carbohydrate antigen

13Anti-SS-A-ab for PM/DM relapse
FIGURE LEGENDS
Figure 1. Patient selection
PM: polymyositis, DM: dermatomyositis, CADM: clinically amyopathic dermatomyositis
Figure 2. Time to relapse in anti-SS-A/Ro antibody-positive and -negative patients with PM/DM
Relapse rates in anti-SS-A/Ro antibody-positive and -negative patients with PM/DM.
PM: polymyositis, DM: dermatomyositis

14