Sarcoidosis involving the musculoskeletal system.

Although sarcoidosis can affect virtually any organ, musculoskeletal involvement is infrequent. Early in the course of the disease, acute polyarthritis may be observed in up to 40% of patients, but this is often self-limited. Chronic or recurrent sarcoid arthritis is rare, affecting only 1 to 4% of patients. Asymptomatic involvement of muscles has been reported in 25 to 75% of patients in small series, but symptomatic involvement of muscles is rare. Although prospective studies assessing the prevalence of muscle involvement in sarcoidosis have not been done, several large retrospective studies suggest that symptomatic muscle involvement occurs in < 0.5% of patients with sarcoidosis. Patterns of sarcoid muscle involvement include chronic, progressive myopathy; nodular or tumorous sarcoidosis affecting muscles; and an acute polymyositis-like syndrome. Corticosteroid therapy is usually efficacious for the acute myositis variant but is less consistently helpful in the other forms (e.g., chronic myopathy or nodules). Similarly, clinically significant involvement of bone is rare (< 2-5%), and is often associated with chronic multisystemic disease, lupus pernio, and chronic uveitis. Unfortunately, osseous sarcoidosis is often unresponsive to therapy. In this review, we discuss the prevalence, clinical features, and management of sarcoidosis involving muscle, joints, and bones.