Case Report: Rare co-occurrence of NMOSD and capillary leak syndrome treated with satralizumab.

This report describes a rare case of neuromyelitis optica spectrum disorder (NMOSD) complicated by systemic capillary leak syndrome (SCLS) and reviews the literature to examine the clinical features, pathogenesis, and therapeutic implications of autoimmune disease-associated SCLS. A 20-year-old woman with NMOSD developed sudden-onset SCLS, presenting with hypotension, hemoconcentration (hematocrit 58.7%), hypoalbuminemia (26 g/L), and pulmonary edema after initial immunotherapy. Cardiogenic and septic shock, as well as pulmonary embolism, were excluded, leading to a diagnosis of SCLS. Intensive treatment with albumin replacement, thoracic drainage, and intravenous immunoglobulin (IVIG, 0.4 g/kg/day) stabilized her condition. Maintenance therapy with satralizumab, an anti-interleukin-6 receptor monoclonal antibody, achieved sustained remission over 1 year. A review of 12 cases (including this case) identified autoimmune diseases-most commonly Sjögren's syndrome (41.7%) and NMOSD (16.7%)-as frequent SCLS comorbidities. Infections (33.3%) and autoimmune flares (25%) were the most common triggers. Multimodal therapy combining glucocorticoids and IVIG, with or without additional immunosuppressants, resulted in clinical improvement in 75% of cases. This report emphasizes that SCLS is a life-threatening complication of autoimmune diseases, particularly NMOSD. Autoimmune disease relapses and infections are common precipitating factors. Prompt diagnosis and intervention are critical. Satralizumab warrants further investigation as a potential therapeutic option for this rare comorbidity.