特発性炎症性筋疾患の診断—筋病理から何が読み取れるか

Diagnosis of Idiopathic Inflammatory Myopathy: A Muscle Pathology Perspective

特発性炎症性筋疾患では臨床所見を重視した分類が広く用いられてきたが，近年病理所見を重視した分類が用いられ，皮膚筋炎，多発筋炎，封入体筋炎，免疫介在性壊死性ミオパチー，抗合成酵素症候群，非特異的な筋炎に分けられる。多発筋炎にはより厳格な基準が用いられ，病理診断では希少となった。免疫介在性壊死性ミオパチーでは新たな自己抗体が発見されている。本稿では病理所見を中心に特発性炎症性筋疾患について概説する。

Abstract

Idiopathic inflammatory myopathies are historically classified into polymyositis and dermatomyositis based on the presence or absence of skin lesions. Recently, however, a more histology-oriented classification into 6 subtypes has been proposed. The subtypes include dermatomyositis, polymyositis, inclusion body myositis, immune-mediated necrotizing myopathy, anti-synthetase syndrome, and non-specific myositis. With strict criteria applied, polymyositis is now extremely rare, while immune-mediated necrotizing myopathy is the most common among all inflammatory myopathies and is often associated with autoantibodies including those for signal recognition particle (SRP) or 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR).