Sarcoidosis is a multisystem granulomatous disorder of unknown etiology that affects individuals worldwide and is characterized pathologically by the presence of noncaseating granulomas in involved organs. It typically affects young adults, and initially presents with one or more of the following abnormalities:
- Bilateral hilar adenopathy
- Pulmonary reticular opacities
- Skin, joint, and/or eye lesions
An overview of the clinical manifestations and diagnosis of sarcoidosis is presented here. Issues relating to pathogenesis and treatment are discussed separately. (See "Pathogenesis of sarcoidosis" and "Treatment of pulmonary sarcoidosis with glucocorticoids" and "Treatment of pulmonary sarcoidosis with alternatives to glucocorticoids".)
The prevalence (estimated at 10 to 20 per 100,000 population) and annual incidence of sarcoidosis are not known with certainty. The disease appears to vary in incidence among geographical regions and can also aggregate in families and specific races, being three to four times more common in blacks . It has been estimated that the lifetime risk of sarcoidosis in blacks in the United States is 2.4 percent, compared with a lifetime risk of 0.85 percent in whites .
In addition, the patient's immunogenetic background may play a role in the clinical manifestations of sarcoidosis, and could underlie the heterogeneity of the illness [3,4]. Epidemiological studies show significant heterogeneity in disease presentation and severity occurs among different ethnic racial groups [5,6]. For example, blacks tend to be affected more acutely and with more severe disease than whites, who tend to present with asymptomatic and chronic disease . There are numerous reports of familial clustering of sarcoidosis. The most prominent finding is linkage to a section within MHC on the short arm of chromosome 6. It appears that several alleles confer susceptibility to disease (HLA DR 11, 12, 14, 15, 17) and others seem to be protective (eg, HLA DRI, DR4, and possibly DQ*0202) .