Apparent diminution of the blastomycin skin test; follow-up of an epidemic of blastomycosis.

Eighteen persons involved in an epidemic of blastomycosis were followed for a period of 3 years. None of the symptomatic patients received antifungal therapy and all recovered spontaneously. During the period of follow-up observation all patients remained in excellent health, and none showed evidence of late exacerbation of the original illness. Two of the originally symptomatic patients continue to show stable pulmonary nodules on chest roentgenograms, whereas the previously abnormal chest roentgenograms in the other patients have become negative. Sixteen of these 18 patients showed a minimum of 5 mm of induration when tested with blastomycin skin test antigen. During the period of observation, the size of this induration tended to diminish.