Objectives: To describe clinicopathologic features of muscular sarcoidosis and the associated sarcoidosis phenotype through a nationwide multicenter study.
Methods: Patients were included if they had histologically proven sarcoidosis and symptomatic muscular involvement confirmed by biological, imaging, or histologic examinations.
Results: Forty-eight patients (20 males) were studied, with a median age at muscular symptoms onset of 45 years (range 18-71). Four patterns were identified: a nodular pattern (27%); smoldering phenotype (29%); acute, subacute, or progressive myopathic type (35%); and combined myopathic and neurogenic pattern (10%). In all patterns, sarcoidosis was multivisceral with a median of 3 extramuscular organs involved (mostly lungs, lymph nodes, eyes, and skin) and a prolonged course with long-term use of corticosteroids and immunosuppressive drugs. Muscular patterns differed according to clinical presentation (myalgia, nodules, or weakness), electromyographic findings, muscular MRI, and response to sarcoidosis treatment. The myopathic and neuromuscular patterns were more severe.
Conclusion: This nationwide study of muscular sarcoidosis allowed the identification of 4 patterns of granulomatous myositis, which differed by phenotypes and the clinical course.