Abstract:

Inflammatory myopathies are a heterogeneous group of immune-mediated diseases that involve skeletal muscle as well as many other organs. The classification of inflammatory myopathies has been based on clinical diagnoses, pathological diagnoses, and autoantibodies, independently. The clinical phenotypes of inflammatory myopathies are characterized by various autoantibodies that are originally detected by RNA or protein immunoprecipitation. However, since the correlation between histological features and autoantibodies had not been fully elucidated, we created the "Integrated Diagnosis Project for Inflammatory Myopathies" in October 2010. Based on our work and previous studies, the three major subsets of inflammatory myopathies defined by autoantibodies are immune-mediated necrotizing myopathy (IMNM), antisynthetase syndrome, and dermatomyositis. IMNM is the pathological entity, characterized by significant necrotic and regeneration muscle fibers with minimal or no inflammatory cell infiltration. The detection of autoantibodies against signal recognition particles or 3-hydroxy-3-methylglutaryl-coenzyme A reductase is important for the diagnosis of IMNM. Antisynthetase syndrome, characterized by myositis, interstitial lung disease, skin rash, arthropathy, and Raynaud phenomenon, is the clinical entity based on the presence of aminoacyl transfer RNA synthetase antibodies. Perifascicular necrosis is a distinctive hallmark of antisynthetase syndrome in muscle pathology. The diagnosis of dermatomyositis is usually based on clinical features of typical skin rash. Several autoantibodies are associated with specific subsets of dermatomyositis. Myxovirus resistance A expression in the myofiber cytoplasm has a better sensitivity for the diagnosis of dermatomyositis compared to perifascicular atrophy. The screening of autoantibodies has clinical relevance for managing patients with inflammatory myopathies.

日本語要旨:

炎症性筋疾患は骨格筋や多臓器を障害する、免疫介在性の不均一な疾患群である。炎症性筋疾患の診断には、臨床診断、病理診断、自己抗体による診断がこれまで個別に用いられてきた。臨床症状は多様な自己抗体によって特徴付けられるが、組織学的な特徴と自己抗体の関連は明らかになっていない。そのため、2010年10月より筋炎の統合的診断研究を開始した。自己抗体によって定義される三大炎症性筋疾患は、免疫介在性壊死性ミオパチー、抗合成酵素症候群、皮膚筋炎である。免疫介在性壊死性ミオパチーは、病理学的に著明な壊死再生を認めるが炎症細胞浸潤は認めない、もしくは最小限であるという特徴を持つ。診断に際しては、抗signal recognition particle (SRP)抗体と抗3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) 抗体の測定が重要である。抗合成酵素症候群は、抗合成酵素抗体を持ち、筋炎、間質性肺炎、皮疹、関節症、レイノー現象という特徴がみられる疾患群である。病理学的には筋束周辺壊死を特徴とする。皮膚筋炎は通常、典型的な皮疹をもとに診断される。特定の型の皮膚筋炎に関連する抗体が存在する。筋線維の細胞質へのミクソウイルス耐性蛋白質 Aの発現は、皮膚筋炎診断において筋束周囲萎縮よりも良好な感度を示す。炎症性筋疾患の患者の診療において、自己抗体のスクリーニングは臨床的に重要である。