Sarcoidosis is a systemic granulomatous disease of unknown etiology. It has diverse clinical manifestations, most frequently including pulmonary disorders. It is associated with immunological abnormalities, the intricacies of which have yet to be clearly delineated. In the immunologically susceptible individual, genetic, environmental, nutritional, and socioeconomic factors may play a governing role in its development. Sarcoidosis is a diagnosis of exclusion established by clinical manifestations, radiologic findings, and histologic evidence of noncaseating epithelioid-cell granulomas in 1 organ. We will discuss parameters that are helpful in making this diagnosis. The diagnostic criteria for sarcoidosis, initially proposed in the 1950s by the International Sarcoidosis Association, demanded that granulomas be present in [greater than or equal to]2 organs in the absence of a disease process that evokes a granulomatous response. A revised descriptive definition introduced by the International Conference on Sarcoidosis in 1975 states that sarcoidosis is a multisystem granulomatous disorder of unknown etiology, most often affecting young adults, in which patients present with hilar lymphadenopathy, pulmonary infiltration, and skin or eye lesions. This definition has remained despite advances in the understanding of the disease. In the first described case of sarcoidosis 120 years ago, it was called "livid papillary psoriasis" by Jonathan Hutchinson. The patient presented with purplish skin lesions and gout and later died of renal failure (1). Hutchinson suspected that this was a variant of mumps.