Blastomycosis

GENERAL PRINCIPLES

• Blastomyces dermatitidis is dimorphic fungus that is endemic to the Ohio and Mississippi River valleys, as well as the Upper Midwestern, South Central, and Southeastern US.

• The organism commonly disseminates, affecting the lungs, skin, bone, brain, and genitourinary tract. Aggressive pulmonary and CNS disease can occur in both immunocompromised and immunocompetent patients.

DIAGNOSIS

Definitive diagnosis is based on culture. Presumptive diagnosis can be made by histopathology and visualization of characteristic yeast forms, or antigen assay in serum or urine. Of note, antigen assay can cross-react with Histoplasma species. Serologic studies can also cross-react with Histoplasma and Cryptococcus species and are unreliable for diagnosis.

TREATMENT

See Table 14-13.