Using local epidemiology to make a difficult diagnosis: a case of blastomycosis

An otherwise well 21-year-old man from Northwestern Ontario presented to our emergency department in Winnipeg, Manitoba, with a 2-month history of cough, progressively increasing dyspnea, hemoptysis and a 15-kg weight loss. His symptoms were worsening despite antibiotic treatment for presumed bacterial pneumonia. His past history included work as a seasonal labourer clearing brush. He was not hypoxic on room air, but his chest radiograph revealed a miliary pattern and bilateral infiltrates. A Mantoux test for tuberculosis was non-reactive, and the sputum gram stain was unremarkable. Empiric therapy was initiated for blastomycosis and the diagnosis was confirmed with a calcofluor stain of the sputum. Although blastomycosis is rare in most regions in North America, there is an unusually high incidence of blastomycosis in Northwestern Ontario. This case highlights the intolerance and utility of knowledge of the local epidemiology in establishing difficult diagnoses of regional importance, such as fungal pneumonias.