Management and Prognosis of Anti-MDA5 Dermatomyositis: Insights from a National Multicenter Cohort.

Background: Anti-melanoma differentiation-associated gene 5 (anti-MDA5) positive dermatomyositis is a distinct subset of idiopathic inflammatory myopathies (IIMs), often associated with unique cutaneous features and interstitial lung disease (ILD). While East Asian cohorts frequently report high mortality due to rapidly progressive ILD (RP-ILD), data regarding Central and Eastern European populations remain scarce. Methods: We conducted a retrospective multicenter study of anti-MDA5 positive Caucasian patients managed at four Hungarian rheumatology centers between 2020 and 2025. Demographic, clinical, serological, and radiological data were analyzed. Antibody profiling was performed using a standardized 16-antigen immunoblot assay. Results: Anti-MDA5 positivity was confirmed in 24 out of 742 patients (3.23%) treated in the four centers. The median age at diagnosis was 49.5 years (range: 24-81). Classic dermatomyositis was the predominant clinical phenotype (75%), followed by clinically amyopathic dermatomyositis (CADM) (12.5%) and polymyositis (12.5%). ILD was identified in 58.3% of patients, presenting with organizing pneumonia (OP), non-specific interstitial pneumonia (NSIP), and usual interstitial pneumonia (UIP) patterns. At diagnosis, median creatine kinase (CK) (193.5 U/L) and C-reactive protein (CRP) (4.24 mg/L) levels remained low even in the ILD group, whereas lactate dehydrogenase (LDH) was elevated in 91.7% of the cohort. Anti-Ro52 positivity (45.8% overall) emerged as a notable predictor of ILD (odds ratio [OR]: 22.5, 95% confidence interval [CI]: 2.10-240.48; p = 0.0045), being present in 71.4% of affected patients. RP-ILD occurred in two patients (8.3%). Therapeutic management followed an early, aggressive strategy, frequently utilizing cyclophosphamide (45.8%) and methotrexate (37.5%), with Janus kinase (JAK) inhibitors or rituximab employed in refractory cases. Overall disease-specific survival was 100% during the study period (median follow-up: 72.0 months); no mortality was directly attributable to IIM-related complications. Conclusions: Our study demonstrates that anti-MDA5 positive dermatomyositis in a Hungarian cohort is characterized by heterogeneous manifestations and a significant association between anti-Ro52 and ILD. The observed dissociation between low CK/CRP and elevated LDH underscores the necessity for a high index of suspicion, with LDH serving as a superior marker for disease activity. While ILD presents a significant risk, early and intensive multi-modal intervention may yield superior survival outcomes in European patients compared to the historical mortality rates reported in Asian cohorts.