Blastomycosis
Blastomycosis is a dimorphic fungal infection acquired by inhaling Blastomyces dermatitidis conidia in the Mississippi and Ohio River valleys, presenting as primary pulmonary infection that can mimic lung cancer or disseminate to skin and bone, diagnosed by direct fungal stain confirmed with culture, antigen, or serology, and treated with itraconazole for mild to moderate disease or liposomal amphotericin B for severe, disseminated, or CNS disease.
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What this article covers
- Overview
Blastomycosis is a systemic infection caused by Blastomyces dermatitidis, a dimorphic, round, budding yeast that grows as a mold in the environment and converts to a yeast form at body temperature.
- Epidemiology
Found primarily along the Mississippi and Ohio River valleys, but also reported as far north as Wisconsin and Minnesota and as far south as Florida.
- Risk factors
Residence in or travel to the Mississippi and Ohio River valleys, or the extended range into Wisconsin, Minnesota, or Florida.
- Pathophysiology
Inhalation of aerosolized Blastomyces dermatitidis conidia deposits the organism in the alveoli.
- Clinical features
Primary pulmonary infection is the hallmark presentation, ranging from an acute pneumonia syndrome (fever, productive cough, pleuritic chest pain) to an indolent chronic pneumonia that can persist for weeks.
- Differential diagnosis
Histoplasmosis: Histoplasmosis shares the Mississippi and Ohio River valley geography and a similar pulmonary presentation, but is confirmed with a urinary antigen assay (85% sensitive in…
- Diagnosis
Blastomycosis is confirmed by direct fungal stain of a clinical specimen (sputum, tissue, or purulent material) showing round, broad-based budding yeast, with the diagnosis then confirmed by culture…
- Management
First, determine disease severity and site of involvement, since this dictates the choice of initial agent.
- Complications
Extrapulmonary dissemination, most often to skin (ulcerative/verrucous lesions) or bone (osteomyelitis).
- Prognosis
Most immunocompetent patients with mild to moderate pulmonary disease do well with itraconazole therapy.
- Prevention
No vaccine exists for blastomycosis; prevention relies on reducing exposure to aerosolized conidia in endemic areas.
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Related articles
- Histoplasmosis
Histoplasma capsulatum is an endemic dimorphic fungus, acquired by inhalation of conidia in the Mississippi and Ohio River valleys and other endemic regions, that most often causes asymptomatic or mild pulmonary infection but can disseminate in immunosuppressed hosts; diagnosis rests on the Histoplasma urinary antigen assay and treatment is itraconazole for mild to moderate disease or liposomal amphotericin B followed by itraconazole for severe or disseminated infection.
- Coccidioidomycosis
Coccidioidomycosis, or valley fever, is a dimorphic fungal infection acquired by inhaling Coccidioides arthroconidia in the southwestern United States, ranging from self-limited pneumonia to disseminated or meningeal disease, diagnosed by culture, histopathology, or serology and treated with fluconazole for symptomatic disease and lifelong fluconazole for meningitis.
- Paracoccidioidomycosis
Paracoccidioidomycosis is a dimorphic fungal infection endemic to Latin America, caused by Paracoccidioides species and identified by its distinctive multiple peripheral-budding "captain's wheel" yeast form on direct microscopy of pulmonary or mucocutaneous specimens. Presentation and treatment closely parallel blastomycosis: itraconazole for mild to moderate disease, liposomal amphotericin B for severe, disseminated, or CNS disease.
- Tuberculosis
Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.
- Osteomyelitis
Osteomyelitis is bone infection from hematogenous seeding or contiguous spread, most often from Staphylococcus aureus, presenting as subacute pain with or without a draining sinus tract and confirmed by bone biopsy culture. Empiric antibiotics are withheld until biopsy in a stable patient, and treatment combines source control with 4 to 6 weeks of culture-directed antibiotics, extended to 6 weeks or indefinite suppression for hardware-associated or chronic disease.