免疫介在性壊死性ミオパチー

Immune-Mediated Necrotizing Myopathy

免疫介在性壊死性ミオパチーは自己免疫性筋炎の一型で，筋病理学的に壊死・再生を主要所見とする。特異自己抗体としてSRP抗体とHMGCR抗体が同定されている。高度の筋線維壊死を反映し，血清クレアチンキナーゼ値は著しく上昇する。筋力低下は高度であることが多い。特に長期経過例で筋ジストロフィーとの鑑別が課題となることがある。治療にはステロイドに加え，免疫抑制薬や免疫グロブリンなどが組み合わせられる。

Abstract

Immune-mediated necrotizing myopathy (IMNM) is a form of autoimmune myositis characterized by the presence of necrotic and regenerating process as a major finding in the muscle. Anti-SRP and anti-HMGCR have been identified as IMNM-specific autoantibodies. Patients with this disease often present with severe muscle weakness and markedly elevated serum creatine kinase (CK) levels. Differentiation from muscular dystrophy is challenging in certain cases. When patients meet the condition “subacute onset”, “hyperCKemia over 1000 IU/L”, and “clinical diagnosis of muscular dystrophy lacking molecular diagnosis”, the possibility of IMNM should be considered. Autoantibody measurement, including of anti-SRP and HMGCR antibodies, is recommended. Treatment with corticosteroid in combination with immunosuppressants, intravenous immunoglobulin, and rituximab can be performed.