For health professionals: Blastomycosis
Find information on blastomycosis for health professionals.
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What health professionals need to know about blastomycosis
Blastomycosis is a pulmonary, cutaneous or disseminated infection caused by the fungus Blastomyces dermatitidis. This fungus exists in mould form in the environment and in yeast form in human tissue.
Blastomycosis is not contagious. There is little evidence of human-to-human transmission, except for rare perinatal or sexual transmission.
Other routes of transmission that have been reported but occur relatively rarely are:
- dog bites
- accidental inoculation
- conjugal transmission
- intrauterine transmission
The mortality rate is:
- 0% to 2% in treated patients
- 42% without treatment
The infection can be asymptomatic or subclinical if the host's immune system is able to limit the disease. Some patients will progress to a chronic form of pneumonia.
Disseminated blastomycosis usually begins with pulmonary infection and can involve the:
- abdominal viscera
- central nervous system
Skin lesions can be nodular, verrucous or ulcerative, often with minimal inflammation. However, they can rapidly grow into a superficial ulceration with a granulomatous base. The lesions are generally located around the face and distal extremities. Abscesses are often subcutaneous but can also involve any organ.
Intrauterine or congenital infections occur rarely. Severe pulmonary and disseminated disease is more likely when cellular immunity is impaired.
Monitor for symptoms.
Diagnosis can be made by microscopic visualization and culture of the organism. Thick-walled, figure-of-eight shaped, broad-based, single-budding yeast forms may be seen in:
- tracheal aspirates
- cerebrospinal fluid
- material from lesions processed with 10% potassium hydroxide or a silver stain
An enzyme immunoassay (EIA) is available for detection of Blastomyces dermatitidis antigen in:
- other body fluids
EIA measures cell wall-derived antigen in serum or urine with good sensitivity, particularly in severe or disseminated disease. However, cross-reactions may occur with other endemic fungal infections.
Treat with appropriate drug therapy. Itraconazole is commonly used for less severe infections. Amphotericin B or amphotericin B deoxycholate are used for more severe infections, sometimes with the addition of itraconazole.
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