Blastomycosis
Blastomycosis is an infection caused by the fungus Blastomyces dermatitidis, which thrives in soil, especially in wooded areas and near waterways. This infection is most prevalent in the central and southeastern United States, Canada, and certain parts of Africa. Primarily affecting the lungs, it can also spread to other body parts, including the skin, bones, and brain. Individuals with outdoor occupations or hobbies, particularly healthy males, are at a higher risk, although cases can occur in all age groups, especially those with weakened immune systems or diabetes. Symptoms may range from asymptomatic to flu-like, including fever, cough, and weight loss, with skin lesions being a significant external indicator. Diagnosis typically involves a combination of blood tests, biopsies, and imaging studies, while treatment may include antifungal medications such as amphotericin B or intraconazole. Prevention focuses on avoiding areas where the fungus is known to exist. If left untreated, blastomycosis can lead to severe complications or be fatal.
Blastomycosis
Anatomy or system affected: Lungs, respiratory system
Also known as: Gilchrist’s disease
Definition
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.
Causes
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.
Risk Factors
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).
Symptoms
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.
Screening and Diagnosis
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.
Treatment and Therapy
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.
Prevention and Outcomes
B. dermatitidis is a microscopic airborne fungus. The best form of prevention is to avoid endemic areas where the fungus is prevalent.
Bibliography
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McKinnell, James A., and Peter G. Pappas. “Blastomycosis: New Insights into Diagnosis, Prevention, and Treatment.” In Fungal Diseases, edited by Kenneth S. Knox and George A. Sarosi. Philadelphia: Saunders/Elsevier, 2009.
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