AB1384 CLINICAL, LABORATORY, AND IMAGING DIFFERENCES BETWEEN IDIOPATHIC MULTICENTRIC CASTLEMAN DISEASE AND IGG4-RELATED DISEASE
Authors: A. González García, G. Starita Fajardo, D. Lucena López, M. Fabregate, N. Bara, J. Jimenez Esteban, G. Peralta Carrero, J. Soto Pérez-Olivares, F. J. Lirola Sánchez, M. López Paraja, M. Peña Rodríguez, L. A. Viteri Noël
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Idiopathic Multicentric Castleman Disease (iMCD) and IgG4-Related Disease (IgG4-RD) are different recognized entities, although their clinical presentations may overlap and cause confusion.<sup>[1]</sup> In addition, the histological similarity of lymph node involvement in both conditions can pose a challenge to clinicians in making the correct diagnosis, as they are exclusive diseases. <h3>Objectives:</h3> The aim of this study was to identify and summarize the key differences between IgG4-RD and iMCD in order to improve understanding and diagnosis process. <h3>Methods:</h3> A retrospective study was conducted on two cohorts of patients with a definite diagnosis of iMCD [2] or IgG4-RD [3], who attended a systemic autoimmune disease unit at a tertiary hospital between 2010 and 2022. We collected and analyzed onset symptoms, as well as demographic and clinical characteristics, laboratory and imaging parameters at diagnosis. Comorbidities were summarized using the age-adjusted Charlson Comorbidity Index (ranging from 0 to 39 points). The study was approved by the institutional Ethics Committee. The variables were described as frequencies (%) and median ± standard deviation or median [interquartile range], as appropriated. Variables with asymmetric distributions were log-transformed. Comparisons were made using Student t test or Mann-Whitney U test, depending on normality. Significance level was p&lt;0.05. IBM SPSS Statistics v24 was used for the analysis. <h3>Results:</h3> A total of n=19 cases of IgG4-RD (31.6% females) and n=14 patients with iMCD (57.1% females) were included. Patients with IgG4-RD were significantly older at diagnosis than those with iMCD (57.6 ± 13.4 vs. 43.7 ± 14.9 years; p=0.008). However, we did not find significant differences between both groups in the mean time from symptom onset to diagnosis (21.6 ± 42.4 vs. 18.1 ± 45.5 months). Patients with igG4-RD had higher age-adjusted Charlson Comorbidity Index compared to iMCD (3.0 [4.0] vs. 0.5 [2.0] points; p=0.006). At the time of diagnosis, malaise was the most commonly reported symptom among iMCD patients (10/14; 71.4%), while only one patient (5.3%) was affected in the IgG4-RD cohort (p&lt;0.001). Likewise, lymphadenopathies (64.3% vs. 5.3%; p&lt;0.001), fatigue (57.1% vs. 5.3%; p=0.002), fever (35.7% vs. 0.0%; p=0.008), and splenomegaly (35.7% vs. 0.0%; p=0.008) were more frequently present in the iMCD group. Meanwhile, orbital (6/19; 31.3%) and parotid inflammation (5/19; 26.3%), followed by dry eye syndrome (4/19; 21.1%), were the most common symptoms among IgG4-RD patients. Serum IgG levels were significantly higher in iMCD compared to IgG4-RD (1670 [458] vs. 1150 [583] mg/dL; p=0.013). Similarly, erythrocyte sedimentation rate (34.5 [65.0] vs. 7.0 [32.0] mm/h; p= 0.016) and C-reactive protein (99.4 [200.0] vs. 2.5 [3.5] mg/L; p = 0.031) were higher among iMCD patients. Regarding coagulation status, fibrinogen levels were also significantly higher in the iMCD group compared to the IgG4RD cohort (554.9 ± 207.2 vs. 364.3 ± 150.1 mg/dL; p=0.039). <h3>Conclusion:</h3> At time of diagnosis, the presence of general symptoms and elevated inflammatory biomarkers, along with lymphadenopathy and splenomegaly, were predominant in iMCD patients. By contrast, glandular involvement, comorbidity burden, and older age were mostly associated with IgG4-RD. When approaching the diagnosis of a patient with systemic involvement and polyadenopathy, it is paramount to characterize inflammatory findings that suggest a higher likelihood of iMCD compared to IgG4-RD. <h3>REFERENCES:</h3> [1] González García A, et al. Idiopathic multicentric Castleman disease and associated autoimmune and autoinflammatory conditions: practical guidance for diagnosis. Rheumatology (Oxford). 2023;62(4):1426-1435. [2] Fajgenbaum DC, et al. International, evidence-based consensus diagnostic criteria for HHV-8-negative/idiopathic multicentric Castleman disease. Blood. 2017; 129(12):1646-1657. [3] Wallace ZS, et al. The 2019 American College of Rheumatology/European League Against Rheumatism Classification Criteria for IgG4-Related Disease. Arthritis Rheumatol. 2020;72(1):7-19. <h3>Acknowledgements:</h3> This study has been partially funded by the Mapfre Foundation through the Ignacio H. de Larramendi 2022 competitive call for research grants. <h3>Disclosure of Interests:</h3> Andrés González García Recordati Rare Diseases Spain, S.L.U., Fresenius Kabi España, S.A., Grisell Starita Fajardo: None declared, David Lucena López: None declared, Martín Fabregate: None declared, Nuria Bara: None declared, Judith Jimenez Esteban: None declared, Gracia Peralta Carrero: None declared, Javier Soto Pérez-Olivares: None declared, Francisco José Lirola Sánchez: None declared, María López Paraja: None declared, Mercedes Peña Rodríguez: None declared, Luis Adrián Viteri Noël: None declared.