Pathophysiology
Clinical meaning
Endemic mycoses (histoplasmosis, blastomycosis, coccidioidomycosis) are caused by dimorphic fungi that exist as moulds in soil and convert to yeast at body temperature. Inhalation of conidia leads to alveolar macrophage phagocytosis. In immunocompetent hosts the cell-mediated immune response (Th1 pathway) typically contains infection as granulomas. In immunocompromised patients or with high inoculum exposure, disseminated disease occurs. Histoplasma capsulatum is endemic to the Ohio and Mississippi River valleys. Blastomyces dermatitidis is found in the Great Lakes and St. Lawrence River regions of Ontario and Quebec. Nurse practitioners must consider travel and occupational exposure history when evaluating chronic pneumonia unresponsive to antibiotics.