Blastomycosis.

Blastomycosis is an endemic mycoses in the central United States caused by a dimorphic fungus, Blastomyces dermatitidis, that exists in nature in mycelial phase and converts to yeast phase at body temperature. The organism may produce epidemics of infection following a point source of infection or sporadic endemic infection. Blastomycosis can be a subclinical illness with subsequent protection against progressive infection afforded by cellular immune mechanisms, but it may present with progressive disease with either pulmonary or extrapulmonary disease or both. Itraconazole has been shown to be the drug of choice for both infections, except in cases of life-threatening infection when amphotericin B should be used.