壊死性筋症の歴史と疾患概念

Immune-Mediated Necrotizing Myopathy: IMNM

免疫介在性壊死性筋症は，筋病理学的な根拠によって2004年に多発筋炎から独立した疾患群である。典型例では亜急性進行性の近位筋優位の筋力低下と著明な血清クレアチンキナーゼ値の上昇を呈し，抗SRP抗体あるいは抗HMGCR抗体が検出される。筋外症状は少なく，緩徐進行性の慢性型は筋ジストロフィー症との鑑別が重要となる。免疫治療が効果を示すが，積極的な治療を行わなければ後遺症を残すことが多く，機能的予後の悪い疾患である。

Abstract

Immune-mediated necrotizing myopathy (IMNM) is a heterogeneous disease that presents with subacute progressive proximal dominant muscle weakness clinically and prominent necrotic muscle fibers without invasion of inflammatory cells pathologically. IMNM is a disease that exclusively affects skeletal muscles, so the serum creatine kinase level usually increases prominently. It is thought to be an autoimmune disease because of the presence of two autoantibodies, anti-SRP and anti-HMGCR. Because muscle involvement is more severe than that in other forms of myositis, its functional prognosis is worse. Several immune-modifying therapies can improve the symptoms; therefore, intensive treatments should be started soon after diagnosis with IMNM.