Delayed diagnosis of osseous blastomycosis in two patients following environmental exposure in nonendemic areas

Abstract

Blastomycosis generally results from inhalation of Blastomyces dermatitidis conidia following exposure to contaminated soil in an endemic area. Primary infections commonly involve the lungs, although secondary dissemination to other body sites may occur. We describe 2 cases of osseous blastomycosis in people living outside the endemic areas. Both patients reported exposure to soil following injury to the knee from occupational activities. Mold isolated from each case was identified as B dermatitidis by micromorphologic characteristics including yeast conversion testing and by a positive AccuProbe Blastomyces dermatitidis test (GenProbe, San Diego, CA). Retrospective review of histologic slides, initially reported as negative, identified rare poorly staining, broad-based budding yeast forms in each case. Both patients were treated successfully with itraconazole with no evidence of recurrent infection after 1 year. These cases illustrate the importance of considering blastomycosis in the differential diagnosis of bony lesions, even though the patient may live outside an endemic area for B dermatitidis. © American Society for Clinical Pathology.