Blastomycosis occurs most often in men infected during occupational or recreational activities outdoors and in a geographically limited area of the south central and midwestern United States and Canada. Disease usually occurs in immunocompetent individuals.
Chronic pulmonary infection is most common and may be asymptomatic. When dissemination takes place, lesions are most frequently seen in the skin, bones, and urogenital system.
Cough, moderate fever, dyspnea, and chest pain are common. These may resolve or progress, with purulent sputum production, pleurisy, fever, chills, loss of weight, and prostration. Radiologic studies, either chest radiographs or CT scans, usually reveal lobar consolidation or masses.
Raised, verrucous cutaneous lesions are commonly present in disseminated blastomycosis. Bones—often the ribs and vertebrae—are frequently involved. Epididymitis, prostatitis, and other involvement of the male urogenital system may occur. Although they do not appear to be at greater risk for acquisition of disease, infection in HIV-infected persons may progress rapidly, with dissemination common.
Laboratory findings usually include leukocytosis and anemia, though these are not specific. The organism is found in clinical specimens, such as expectorated sputum or tissue biopsies, as a thick-walled cell 5–20 mcm in diameter that may have a single broad-based bud. It grows readily on culture. A urinary antigen test is available, but it has considerable cross reactivity with other dimorphic fungi; it may be useful in monitoring disease resolution or progression. The quantitative antigen enzyme immunoassay may be helpful in the diagnosis of CNS disease. A serum enzyme immunoassay based on the surface protein BAD-1 has much better sensitivity and specificity than the urinary antigen test, but it is not yet commercially available.
Itraconazole, 200–400 mg/day orally for at least 6–12 months, is the therapy of choice for nonmeningeal disease, with a response rate of over 80% (Table 36–1). Liposomal amphotericin B, 3–5 mg/kg/day intravenously, is given initially for severe disease, treatment failures, or CNS involvement.
Clinical follow-up for relapse should be made regularly for several years so that therapy may be resumed or another drug instituted.
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