Sarcoidosis is a systemic disease of unknown origin that is characterized by formation of noncaseating granulomas in affected organs of the body. For clinical purposes, the diagnosis can be considered established if the following three criteria are satisfied: (1) a compatible clinical or radiological picture, or both; (2) histological evidence of noncaseating granulomata; and (3) negative bacterial and fungal studies of biopsied tissue, sputum, and other appropriate body fluids.1 Evidence of only one feature is misleading, since clinical or radiological manifestations present too wide a differential diagnosis, and histological evidence of noncaseating granulomata may be produced by many bacterial, viral, fungal, parasitic, and chemical agents.
HISTOLOGICAL EVIDENCE AND THE KVEIM TEST
A difficult problem is encountered if histological evidence reveals a "local sarcoid reaction." An equally difficult situation arises when a patient with typical clinical evidence of sarcoidosis fails to show characteristic granulomatous reaction but displays either only a