Juvenile Systemic Sclerosis in a Single Center: Clinical Features, Capillaroscopic Findings, Immunological Profile,...

Background/Objectives: Juvenile systemic sclerosis (jSSc) is a rare, chronic autoimmune disease with limited pediatric data. We aimed to characterize the demographic, clinical, immunological, and microvascular features of a Russian cohort of children with jSSc, and to evaluate treatment outcomes and predictors of escalation to biologic therapy. Methods: A retrospective single-center study of 40 children with jSSc (36 girls, 4 boys) followed over a 20-year period (2004-2024) was conducted. Clinical assessment included the modified Rodnan Skin Score (mRSS) and the Juvenile Systemic Sclerosis Severity Score (J4S). Nailfold capillaroscopy (NFC) was performed in 12 patients. Autoantibody profiling was available for 30 patients. Two first-line regimens were compared: glucocorticosteroids with penicillamine (PA, n = 19) versus glucocorticosteroids with DMARDs (methotrexate, mycophenolate mofetil, or cyclophosphamide; n = 21). Predictors of switching to biologic therapy were identified using binary logistic regression. Results: Median age at onset was 9.0 years (IQR 6.0-10.0), and diagnostic delay was 12.0 months (IQR 4.0-24.0). Diffuse cutaneous jSSc predominated (82.5%). Gastrointestinal involvement was detected in 82.5%, Raynaud's phenomenon in 87.5%, and ILD in 37.5%. NFC revealed reduced capillary density (5.26 ± 1.33/mm). Giant capillaries were observed exclusively in males (4/4 vs. 0/8, p = 0.002). DMARD-based regimens were associated with better outcomes than PA, particularly for joint involvement. Eleven patients (27.5%) were switched to biologic therapy, primarily rituximab. ILD and J4S > 15 were the strongest predictors of switching (probability 60-61% vs. 8-15%, p < 0.001). The 5-year survival was 100%; the estimated 10-year survival was 71.4%, although the latter estimate should be interpreted cautiously because of the small number of events and loss to follow-up. Conclusions: In our cohort, children with jSSc present predominantly with diffuse cutaneous involvement. Male patients may be at risk for more severe microvascular changes, possibly related to diagnostic delay. ILD and J4S > 15 were associated with escalation to biologic therapy, and earlier switching to rituximab may be beneficial in refractory patients. Future prospective multicenter studies are needed to validate these findings.