Blastomyces dermatididis (Chicago Disease, Gilchrist's disease, North American Blastomycosis)

General: Endemic to the southeastern and southcentral U.S., and found particularly in soil enriched with decomposing organic debris. It is also common among dogs, as well as horses, cows, cats, bats, and lions.

Clinical: Acquired via inhilation of conidia, which develop into the yeast form in the lungs. Symptoms may develop in 21-109 days (~45), similar to a bacterial pneumonia, although ~half of infections are asymptomatic. May affect essentially any organ, usually in indolent fashion, with skin as the most common extra-pulmonary dissemination site. Rarely, may be primary cutaneous. It rarely resolves spontaneously; antifungal therapy is indicated for all clinical presentations.

• Normal:
• Abnormal:

Resistance:

Morphology: Produces an acute suppurative and granulomatous response, with yeast forms usually demonstrable at the edge of abscesses. Granulomas predominate in lung infections. Yeasts demonstrate broad-based budding and range in size from 8-30um (~15um); the larger yeasts may be confused with Coccidiodes immitis or Cryptococcus neoformans. Best seen with PAS with diastase; not seen well with H&E, except intracellular yeasts in giant cells in the skin, which appear as punched out holes.

Growth characteristics:

Common/important pathogens: