A case of coccidioidomycosis diagnosed by exoantigen testing.

A case of coccidioidomycosis is described which was caused by a pigmented fungus that failed to produce arthroconidia. Exoantigen testing showed that the isolate produced an antigen that gave a line of identity with Coccidioides (C.) immitis. The formation of spherules in a guinea pig testis confirmed the identity of the isolate as C. immitis. The patient's serum was found to have antibodies that reacted in complement fixation and immunodiffusion tests to C. immitis antigens. The exoantigen test results were responsible for the diagnosis of coccidioidomycosis in this case.