What is blastomycosis?
Blastomycosis is an infection caused by Blastomyces dermatitidis , a fungus typically found in soil. It is endemic to the central and southeastern United States, Canada, and parts of Africa. This type of infection primarily affects the lungs but may spread to other parts of the body.
B. dermatitidis is a dimorphic fungus that exists as either a mold or a yeast, depending on the environment where it is found. The fungus is in mold form in wooded areas and waterways. Inhalation of fungal spores into the lungs causes a respiratory infection known as pulmonary blastomycosis. Once inside the body, the spores transform into a phagocytosis-resistant yeast form that creates cavities and then disperses. The most common extrapulmonary site of infection is the skin, followed by the bones, the prostate and other genitourinary organs, and the brain.
All ages may be affected by the disease; however, the majority of reported cases involve healthy males with an outdoor occupation or hobby. Persons with diabetes mellitus or those with weakened immune systems, including organ transplant recipients and those on immunosuppressants, are more likely to have a severe form of the disease. Atypical for fungal infections, blastomycosis is not more likely to appear in persons with acquired immunodeficiency syndrome (AIDS).
Some persons with pulmonary blastomycosis are asymptomatic, while others may have flulike symptoms that include fever, chills, myalgia, headache, cough, chest pain, weight loss, and fatigue. Extrapulmonary blastomycosis of the skin is indicated by ulcerated lesions on the face, neck, and extremities and is a significant indication of the disease. As the disease progresses, pain and lesions may occur on the bones, genitalia, parts of the central nervous system, and organs. Persons with severe disease may show symptoms simulating bacterial pneumonia, tuberculosis, lung cancer, or adult respiratory distress syndrome.
Blastomycosis is a rare systemic infection. Primary care physicians often consult with an infectious disease specialist for diagnosis and treatment. Diagnostic tests include blood and urine analyses, tissue biopsy, sputum culture, chest X ray, and bronchoscopy. Definitive diagnosis of blastomycosis requires culture and analysis of infected tissue under a microscope.
Persons with blastomycosis should be treated based on the extent and severity of the disease. Amphotericin B and intraconazole are the drugs of choice. Oral intraconazole is recommended for persons with pulmonary blastomycosis. Intravenous amphotericin B is recommended for persons with severe disease. A blastomycosis infection has the potential to be fatal if untreated.
B. dermatitidis is a microscopic airborne fungus. The best form of prevention is to avoid endemic areas where the fungus is prevalent.
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