Hikari Higa

Rationale: Anti-melanoma differentiation–associated gene 5 (anti-MDA5) antibody-positive dermatomyositis is frequently complicated by rapidly progressive interstitial lung disease and may present with life-threatening hemophagocytic syndrome, a critical but often under-recognized complication. Prompt diagnosis and intervention are essential to improve patient outcomes. Patient concerns: A 38-year-old Japanese woman presented with fever, arthralgia, erythema, and elevated liver enzymes. Physical examination revealed chilblain-like erythema, Gottron and reverse Gottron signs, and tenderness in the thighs. Diagnoses: Blood tests revealed pancytopenia and elevated soluble interleukin-2 receptor and ferritin levels. Bone marrow aspiration showed macrophage activation and hemophagocytosis. Imaging revealed ground-glass opacities in both lower lung lobes and bilateral thigh myositis. The presence of anti-MDA5 antibodies led to the diagnosis of anti-MDA5-positive dermatomyositis complicated by autoimmune-related hemophagocytic syndrome. Liver biopsy suggested cytokine storm-mediated hepatocyte damage and macrophage infiltration. Interventions: The patient received steroid pulse therapy, tacrolimus, and intravenous cyclophosphamide. Outcomes: Pancytopenia and liver dysfunction improved significantly following treatment. The patient was transitioned to outpatient care. After 4 years of follow-up, during which she received 6 courses of cyclophosphamide, steroids, and tacrolimus were successfully tapered off, and she remained in remission without recurrence. Lessons: This case underscores the importance of early recognition of hemophagocytic syndrome in patients with anti-MDA5-positive dermatomyositis. Prompt bone marrow evaluation and aggressive immunosuppressive therapy may lead to favorable long-term outcomes. Further studies are warranted to establish standardized treatment strategies for autoimmune-related hemophagocytic syndrome.