The cause of the disease is unknown. Tissue samples from affected organs show clusters of immune cells (macrophages, lymphocytes, and multinucleated giant cells). These clusters are called granulomas. Possible causes include a hypersensitive response to some factor in the environment, a genetic predisposition, or an extreme immune response to infection. The incidence varies widely according to race and sex. The disease is most common among North Americans of African heritage and Northern European Caucasians. Women of African heritage are affected more than men of African heritage. The onset of the disease usually occurs in people between 30 and 50 years old. Sarcoidosis is very rare in young children.
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