Sarcoidosis: a rheumatologist's perspective.

Sarcoidosis is a systemic disorder of unknown etiology, which may involve various tissues and organs and is characterized by a noncaseating granuloma reaction. While pathogenesis is not yet clear, cellular immune system activation and nonspecific inflammatory response occur secondarily to several genetic and environmental factors. T helper 1-cells and macrophage-derived pro-inflammatory cytokines stimulate the inflammatory cascade and formation of granuloma occurs as a result of tissue permeability, cell influx, and local cell proliferation. The different prevalence, clinical results, and disease course observed in different races and ethnic groups, is an indicator of the heterogeneous nature of the disease. Sarcoidosis may mimic and/or may occur concomitantly with numerous primary rheumatic diseases. This disease most commonly presents with bilateral hilar lymphadenopathy, pulmonary infiltrations, and skin and eye lesions. Locomotor system involvement is observed at a range of 15% and 25%. Two major joint involvements have been described: acute and chronic form. The most common form, the acute form, may be the first sign of sarcoidosis and present with arthralgia, arthritis, or periarthritis. Chronic sarcoid arthritis is usually associated with pulmonary parenchymal disease or other organ involvement and occurs rarely. While asymptomatic muscular involvement is reported between 25% and 75%, symptomatic muscular involvement is very rare. Symptomatic myopathy may present as three different types: chronic myopathy, palpable nodular myositis, or acute myositis. Even if rare, 2-5% of cases may exhibit osseous involvement and it is frequently associated with lupus pernio, chronic uveitis, and multisystemic disease. Sarcoidosis was reported together with different rheumatologic diseases. There are studies showing that sarcoidosis may mimic the clinical and laboratory findings of these disorders. Nonsteroidal anti-inflammatory drugs and corticosteroids are used for treating the symptoms of rheumatologic findings. In patients who are unresponsive to corticosteroids, immunosuppressive and anti-tumor necrosis factor alpha drugs may be used. In this review, the incidence of rheumatologic symptoms, the clinical findings, and the treatment of rheumatologic manifestations of sarcoidosis are discussed.