Objective:To analyze the clinical characteristics and treatment outcomes of children with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody-mediated necrotizing myopathy, and to explore early identification and management strategies to provide reference for clinical diagnosis and treatment.Methods:A retrospective analysis was conducted on the clinical data and treatment outcomes of 10 pediatric patients with anti-HMGCR antibody-mediated necrotizing myopathy admitted to the Department of Rheumatology, Children′s Hospital of Fudan University from December 2020 to December 2024. Statistical description was performed using SPSS 22.0.Results:Among the 10 patients, the male-to-female ratio was 1:4, the age of onset was (7.2±4.0) years, and the disease duration at diagnosis was (22.2±19.6) months. None had a history of statin exposure. Six patients presented with muscle weakness, and4 were diagnosed due to asymptomatic elevation of creatine kinase (CK); 4 had dermatomyositis-like rashes. All patients showed significantly elevated CK levels [median 3 291(1 969, 8 776)U/L] and underwent muscle biopsy. Histopathological findings revealed myofiber degeneration, necrosis, and regeneration in all cases, with inflammatory infiltration in 9 cases, MHC-Ⅰ positivity in all, and C5b-9 positivity in 9 cases. The median follow-up duration was (15.7±6.3) months. At the last follow-up, muscle strength was normal or nearly normal, and the CK median value had decreased to 977.5 (211.0, 3 536.0) U/L.Conclusion:For patients with suspected idiopathic inflammatory myopathy and significantly elevated CK, muscle-specific antibody testing-including anti-HMGCR-and muscle biopsy should be performed promptly regardless of the presence of skin rash, to ensure accurate diagnosis and guide treatment, thereby avoiding misdiagnosis or missed diagnosis.

Objective:To analyze the clinical characteristics and treatment outcomes of children with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody-mediated necrotizing myopathy, and to explore early identification and management strategies to provide reference for clinical diagnosis and treatment.Methods:A retrospective analysis was conducted on the clinical data and treatment outcomes of 10 pediatric patients with anti-HMGCR antibody-mediated necrotizing myopathy admitted to the Department of Rheumatology, Children′s Hospital of Fudan University from December 2020 to December 2024. Statistical description was performed using SPSS 22.0.Results:Among the 10 patients, the male-to-female ratio was 1:4, the age of onset was (7.2±4.0) years, and the disease duration at diagnosis was (22.2±19.6) months. None had a history of statin exposure. Six patients presented with muscle weakness, and4 were diagnosed due to asymptomatic elevation of creatine kinase (CK); 4 had dermatomyositis-like rashes. All patients showed significantly elevated CK levels [median 3 291(1 969, 8 776)U/L] and underwent muscle biopsy. Histopathological findings revealed myofiber degeneration, necrosis, and regeneration in all cases, with inflammatory infiltration in 9 cases, MHC-Ⅰ positivity in all, and C5b-9 positivity in 9 cases. The median follow-up duration was (15.7±6.3) months. At the last follow-up, muscle strength was normal or nearly normal, and the CK median value had decreased to 977.5 (211.0, 3 536.0) U/L.Conclusion:For patients with suspected idiopathic inflammatory myopathy and significantly elevated CK, muscle-specific antibody testing-including anti-HMGCR-and muscle biopsy should be performed promptly regardless of the presence of skin rash, to ensure accurate diagnosis and guide treatment, thereby avoiding misdiagnosis or missed diagnosis.