Blastomycosis

Definition

Definition of Blastomycosis
Blastomycosis (also known as "North American blastomycosis," "Blastomycetic dermatitis," and "Gilchrist's disease" is a fungal infection caused by the organism Blastomyces dermatitidis. Endemic to portions of North America, blastomycosis causes clinical symptoms similar to histoplasmosis.

Symptoms

Symptoms of Blastomycosis
Lung infection may not cause any symptoms. Symptoms may be seen if the infection spreads. Symptoms may include:

1. Bone pain
2. Chest pain
3. Cough (may produce brown or bloody mucus)
4. Fatigue
5. Fever
6. General discomfort, uneasiness, or ill feeling (malaise)
7. Joint pain
8. Muscle pain
9. Night sweats
10. Rash
11. Shortness of breath
12. Sweating
13. Unintentional weight loss

Causes

Causes of Blastomycosis
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.

Diagnosis

Diagnosis of Blastomycosis
Once suspected, the diagnosis of blastomycosis can usually be confirmed by demonstration of the characteristic broad based budding organisms 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.

Treatment

Treatment of Blastomycosis
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.

Prognosis

Prognosis of Blastomycosis
Mortality rate in treated cases

1. 0-2% in treated cases among immunocompetent patients
2. 29% in immunocompromised patients
3. 40% in the subgroup of patients with AIDS
4. 68% in patients presenting as acute respiratory distress syndrome (ARDS)

Prevention

Prevention of Blastomycosis
Avoiding travel to areas where the infection is known to occur may help prevent exposure to the fungus, but this may not always be possible.