Juvenile dermatomyositis in Latvia: clinical, radiologic, laboratory, and therapeutic findings from 2010 to 2025.

Background: Juvenile dermatomyositis (JDM) is a rare autoimmune inflammatory myopathy characterized by inflammation of skeletal muscle and skin, with potential multisystem involvement. Long-term population-based data remain limited, particularly in small countries such as Latvia. This retrospective analysis (2010-2025) describes epidemiological, clinical, laboratory, and imaging findings among children with JDM in Latvia. Materials and methods: We conducted a single-center retrospective case series of all children diagnosed with JDM at the Children's Clinical University Hospital, Riga, between 2010 and 2025. Diagnosis was established according to the 2017 EULAR/ACR classification criteria. Clinical features, laboratory parameters, imaging findings, treatment strategies, and outcomes were analyzed. Results: Seventeen children were identified (58.8% female), with a median age at diagnosis of 6 years (range, 2-16 years). The mean annual incidence was 0.32 per 100,000 children. Disease was most frequently diagnosed in winter (52.9%). The median time from symptom onset to diagnosis was 90 days. The most common clinical features were symmetric proximal muscle weakness (70.6%), generalized weakness (70.6%), and characteristic skin manifestations (58.8%), including heliotrope rash and Gottron's papules. Elevated lactate dehydrogenase (LDH) and erythrocyte sedimentation rate (ESR) were observed in 94% of children, whereas creatine phosphokinase (CPK) elevation occurred in 35%. Muscle magnetic resonance imaging demonstrated inflammatory changes consistent with myositis when clinically indicated. One child with JDM developed interstitial lung disease, one had gastrointestinal vasculitis, and one had clinically amyopathic JDM. All children received pharmacological treatment, most commonly glucocorticosteroids and non-steroidal anti-inflammatory drugs, with methotrexate used as the principal steroid-sparing agent. Remission within the first year was achieved in 70.6% of children using conventional therapy alone. Two children received biologic therapy. No mortality or macrophage activation syndrome was observed. Conclusions: This retrospective study covering 2010-2025 shows that JDM in Latvia generally presents similarly to that described in other cohorts of children. Proximal muscle weakness and characteristic skin findings were common, while CPK elevation was observed in only a subset of children. Most children responded well to treatment with glucocorticosteroids and methotrexate, with remission achieved in the majority within the first year and only rare need for biologic therapy. Muscle MRI was particularly helpful in selected cases when laboratory findings were inconclusive. Overall outcomes were favorable, with few severe complications and no mortality.