シンポジウム8：筋炎診療の未来図：治療戦略の最適化を目指して
診断難渋例から学ぶ筋炎の統合的診断アプローチ
2026 年 43 巻 3 号 p. 303-306
詳細
2026 年 43 巻 3 号 p. 303-306
Background : Myositis–specific autoantibodies (MSAs) are essential for the diagnosis and classification of idiopathic inflammatory myopathies (IIM). However, comprehensive autoantibody testing is not always available, and serological findings may be discordant with clinical phenotypes. Diagnostic strategies beyond serology therefore remain necessary.
Methods : We retrospectively analyzed three diagnostically challenging IIM cases in which clinical features, muscle magnetic resonance imaging (MRI), and muscle pathology were integrated to establish final diagnoses.
Results : Case 1 involved a man with long–standing asymptomatic hypercreatine kinaseemia initially suggestive of a hereditary myopathy ; muscle MRI and biopsy revealed inflammatory changes, and anti–signal recognition particle antibody confirmed immune–mediated necrotizing myopathy. Case 2 was an elderly woman with typical dermatomyositis skin manifestations in whom muscle pathology, particularly sarcoplasmic myxovirus resistance protein A expression, was decisive and later supported by anti–TIF1–γ and anti–Mi–2 antibody positivity. Case 3 presented with interstitial lung disease and myositis despite negative standard anti–aminoacyl–tRNA synthetase antibody screening ; extended testing identified anti–OJ antibody, confirming antisynthetase syndrome.
Conclusions : Muscle pathology and imaging remain indispensable for accurate IIM diagnosis, particularly in seronegative or diagnostically discordant cases, enabling precise disease classification and timely treatment.
