筋サルコイドーシス

Muscular Sarcoidosis

筋サルコイドーシスは，非乾酪性類上皮細胞肉芽腫が筋組織内で免疫学的機序により形成される原因不明の肉芽腫性筋炎である。その多くが無症候性で画像検査や筋生検により発見される。症候性（＝サルコイドミオパチー）は稀な病態で，進行性の筋力低下や筋萎縮を呈する場合があり，早期診断・早期治療が求められる。診断には画像検査とともに丹念な筋病理解析が必須である。ステロイド治療が第1選択であるが，難治例もあり，依然治療方針は確立しておらず今後の課題である。

Abstract

Muscular sarcoidosis is a granulomatous myopathy of unknown etiology characterized by the presence of non-caseating granulomas associated with sarcoidosis. Asymptomatic muscle involvement is revealed by imaging findings in majority of the patients with muscular sarcoidosis. Symptomatic muscular sarcoidosis, namely sarcoid myopathy, is a rare condition, and three distinct clinical types are recognized: nodular myopathy, acute myopathy, and chronic myopathy. Patients often present with myalgia, progressive weakness, and atrophy of the proximal muscles of the extremities. In order to confirm a diagnosis of sarcoid myopathy and distinguish it from other muscle disorders, muscle biopsy is the most effective and useful method even in the absence of weakness or myalgia. In addition, magnetic resonance imaging, gallium-67 citrate scintigraphy, and fluorodeoxyglucose-positron emission tomography provide significant information for diagnosis. Immunomodulatory therapy, including corticosteroids, plays an important role in preventing progression. However, effective therapeutic strategies for sarcoid myopathy have not been established yet and need to be explored in the future.