
1. a disseminated or localized infection with Blastomyces spp.
2. infection with any yeastlike organism.
An infection resulting from the fungus Blastomyces dermatitidis(North American blastomycosis) or Blastomyces brasiliensis(South American blastomycosis); characterized by chronic suppurative lesions. The disseminated form is usually fatal.

Blastomycosis. (Neville/Damm/Allen/Bouquot, 2002, Courtesy of Dr. William Welton)

| Blastomycosis | |
|---|---|
| Classification and external resources | |
Blastomyces dermatitidis, the causative agent of blastomycosis. |
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| ICD-10 | B40 |
| ICD-9 | 116.0 |
| DiseasesDB | 1439 |
| MedlinePlus | 000102 |
| eMedicine | med/231 ped/254 |
| MeSH | D001759 |
Blastomycosis (also known as "North American blastomycosis," "Blastomycetic dermatitis," and "Gilchrist's disease"[2]:319) is a fungal infection caused by the organism Blastomyces dermatitidis. Endemic to portions of North America, blastomycosis causes clinical symptoms similar to histoplasmosis.[3]
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Contents
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Blastomycosis can present in one of the following ways:
Infection occurs by inhalation of the fungus from its natural soil habitat. Once inhaled in the lungs, they multiply and may disseminate through the blood and lymphatics to other organs, including the skin, bone, genitourinary tract, and brain. The incubation period is 30 to 100 days, although infection can be asymptomatic.
Once suspected, the diagnosis of blastomycosis can usually be confirmed by demonstration of the characteristic broad based budding organisms[4] in sputum or tissues by KOH prep, cytology, or histology. Tissue biopsy of skin or other organs may be required in order to diagnose extra-pulmonary disease. Blastomycosis is histologically associated with granulomatous nodules. Commercially available urine antigen testing appears to be quite sensitive in suggesting the diagnosis in cases where the organism is not readily detected. While culture of the organism remains the definitive diagnostic standard, its slow growing nature can lead to delays in treatment of up to several weeks.
However, sometimes blood and sputum cultures may not detect blastomycosis[5]; lung biopsy is another option, and results will be shown promptly.
Itraconazole given orally is the treatment of choice for most forms of the disease. Ketoconazole may also be used. Cure rates are high, and the treatment over a period of months is usually well tolerated. Amphotericin B is considerably more toxic, and is usually reserved for immunocompromised patients who are critically ill and those with central nervous system disease. Fluconazole has also been tested on patients in Canada.
Mortality rate in treated cases
In the United States, blastomycosis is endemic in the Mississippi river and Ohio river basins and around the Great Lakes. The annual incidence is less than 1 case per 100,000 people in Mississippi, Louisiana, Kentucky, and Arkansas. The cases are greater in northern states such as Wisconsin, where from 1986 to 1995 there were 1.4 cases per 100,000 people.[6] It also frequently affects hunting dogs in northern Wisconsin and the upper Mississippi and Wisconsin Rivers.[7]
In Canada, most cases of blastomycosis occur in Northwestern Ontario, particularly around the Kenora area. The moist, acidic soil in the surrounding woodland harbors the fungus.
Blastomycosis is distributed internationally; cases are sometimes reported from Africa.[8]
Blastomycosis was first described by Thomas Casper Gilchrist[9] in 1894 and sometimes goes by the eponym Gilchrist's disease.[10] It is also sometimes referred to as Chicago Disease.
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