Sarcoidosis in autoimmune disease.

Sarcoidosis is a multisystem granulomatous disease of unknown etiology. Sarcoidosis coexisting with connective tissue diseases, once considered rare, complicates various such disorders, including rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, Sjögren's syndrome, and the spondyloarthropathies. Symptoms common to sarcoidosis and autoimmune disease include keratoconjunctivitis sicca, weight loss, fever, lymphadenopathy, pulmonary complaints, and cutaneous lesions. Consequently, the diagnosis of sarcoidosis in association with connective tissue disease is often difficult and may require biopsy of the lung, liver, skin, lymph node, muscle, or bone marrow for pathological confirmation. Abnormalities of immune function as well as autoantibody production, including rheumatoid factor and antinuclear antibodies, are seen in sarcoidosis and in connective tissue diseases, suggesting a common immunopathogenic mechanism. The severity and course of sarcoidosis associated with autoimmune disease is variable. The incidence of sarcoidosis in association with rheumatic disease may be underestimated if new symptoms of sarcoidosis are attributed to the primary rheumatic disease and a secondary diagnosis is not pursued.