Information for Healthcare Professionals About Blastomycosis

Blastomycosis is asymptomatic in approximately 50% of cases.¹ Symptomatic persons usually present 3 weeks to 3 months after exposure. The clinical presentation of acute pulmonary blastomycosis is often non-specific; symptoms may include:^2,3

• Fever
• Cough
• Night sweats
• Myalgia
• Arthalgia
• Anorexia
• Chest pain
• Fatigue

Acute pulmonary blastomycosis can progress to acute respiratory distress syndrome (ARDS). Approximately 25% to 40% of symptomatic cases will develop extrapulmonary infection, which typically manifests as cutaneous, osteoarticular, genitourinary, or central nervous system disease.⁴

Blastomycosis is caused by the dimorphic fungus Blastomyces. Phylogenetic analysis suggests that some infections in the United States previously classified as B. dermatitidis might be a new species, B. gilchristii. Furthermore, recent infections in the western United States have been attributed to a newly described species B. helicus.^5,6

The fungus lives in the environment, particularly in soil and decaying organic matter such as wood or leaves. Endemic areas in the United States include the midwestern, south-central, and southeastern states, particularly areas surrounding the Ohio and Mississippi River valleys, the Great Lakes, the Saint Lawrence River, and the western United States.^7,8 Parts of Canada are also endemic, particularly Ontario,⁷ Quebec,⁹ and Manitoba.¹⁰ Autochthonous cases have also been reported from Africa¹¹ and India.¹²

Blastomycosis is typically acquired via inhalation of airborne conidia. Primary cutaneous blastomycosis is uncommon but can result from traumatic inoculation.¹³

People in endemic areas, particularly those who have occupations or participate in activities that expose them to soil, may beat increased risk. Immunocompromised persons and people in some racial/ethnic groups may be at higher risk for developing severe forms of the disease.¹⁵

• Antigen detection: Enzyme immunoassay (EIA) is typically performed on urine or serum, but can also be used on bronchoalveolar lavage fluid. Cross-reactions can occur with histoplasmosis and other fungal diseases.
• Antibody tests: Antibody tests such as immunodiffusion (ID) and complement fixation (CF) are available, but have low sensitivity and specificity. Antibody EIAs have also been developed and have better sensitivity and specificity but can be difficult to interpret.
• Culture: The gold standard for diagnosing blastomycosis. A commercially available DNA probe (AccuProbe, GenProbe Inc.) can be used to confirm.
• Microscopy: Important for detection of yeast in tissue or respiratory secretions.
• Polymerase chain reaction (PCR): Blastomyces PCR can be used to confirm culture or histopathologic identification and on blood to detect disseminated disease.

Amphotericin B is recommended for moderate to severe disease, central nervous system disease, immunosuppressed patients, or pregnant patients. Itraconazole is recommended for mild to moderate disease and step-down therapy. Therapeutic drug monitoring should be considered for certain antifungals like itraconazole when treating blastomycosis. For more detailed treatment guidelines, please refer to the Infectious Diseases Society of America’s Clinical Practice Guidelines for the Management of Blastomycosis

People in endemic areas, particularly those who have occupations or participate in activities that expose them to soil. Immunocompromised persons may be at higher risk for developing severe forms of the disease.¹⁴

Blastomycosis is reportable in certain states. Check with your local, state, or territorial public health department for more information about disease reporting requirements and procedures in your area. Get blastomycosis statistics.