Blastomycosis is an infection caused by inhaling microscopic particles (spores) produced by the fungus Blastomyces dermatitidis. Blastomycosis maybe limited to the lungs or also involve the skin and bones. In its most severe form, the infection can spread throughout the body and involve many organ systems.

Although primarily an airborne disease, farmers and gardeners may become infected from contact with spores in the soil through cuts and scrapes. The fungus that causes the disease is found in moist soil and wood in the southeasternUnited States, the Mississippi River Valley, southern Canada, and Central America. Blastomycosis is also called Gilchrist's disease, Chicago disease, orNorth American blastomycosis. Canine blastomycosis, a common dog disease, iscaused by the same fungus that infects humans. However, people do not get this disease from their dogs except only very rarely through dog bites.

Blastomycosis is a rare disease infecting only about 4 in every 100,000 people. It is at least six times more common in men than in women and tends to most often affect children and individuals in the 30-50 year old age group. People who have diabetes mellitus or who are taking drugs that suppress the immune system (immunocompromised) are more likely to develop blastomycosis. Although people with AIDS can get blastomycosis because of their weakened immune system, blastomycosis has not been one of the more common fungal infections associated with AIDS.

Once inhaled, the spores of B. dermatitidis can lodge in the lungs andcause a local inflammation. This is known as primary pulmonary blastomycosis. The disease does not spread from person to person. In the early stages, symptoms may include a dry cough, fever, heavy sweating, fatigue, and a generalfeeling of ill health. In approximately 25% of blastomycosis cases, only thelungs are affected. As the disease progresses, small lesions form in the lungs causing the air sacs deep within the lungs (alveoli) to break down and formsmall cavities.

In another 35% of infected people, the disease involves both the lungs and the skin. Bumps develop on the skin, gradually becoming small, white, crusted blisters filled with pus. The blisters break open, creating abscesses that donot heal. Approximately 19% of infected people have skin sores without infection in the lungs.

The remaining 20% of the infected population has blastomycosis that has spread to other systems in the body. Symptoms may include pain and lesions on oneor more bones, the male genitalia, and parts of the central nervous system. The liver, spleen, lymph nodes, heart, adrenal glands, and digestive system may also be infected.

A positive diagnosis of blastomycosis is made when the fungus B. dermatitidis is identified by direct microscopic examination of body fluids such as sputum and prostate fluid, or in tissue samples (biopsies) from the lung orskin. Another way to diagnose blastomycosis is to culture and isolate the fungus from a sample of sputum. Chest x rays are used to assess lung damage, but alone cannot lead to a definitive diagnosis of blastomycosis, because any damage caused by other diseases, such as by pneumonia or tuberculosis, may appear similar on the x ray. Because its symptoms vary widely, blastomycosis isoften misdiagnosed.

Blastomycosis must be treated or it will cause death. Treatment with the fungicidal drug ketoconazole (Nizoral) taken orally is effective in about 75% ofpatients. Amphotericin B (Fungizone) given intravenously is also very effective, but it has more toxic side effects than ketoconazole. Treatment with amphotericin B usually requires hospitalization, and the patient may also receiveother drugs to minimize the its side effects.

Alternative treatment for fungal infections focuses on creating an internal environment where the fungus cannot survive. This is accomplished by eating adiet low in dairy products, sugars, including honey and fruit juice, and foods like beer that contain yeast, and a diet high in uncooked and unprocessed foods.

Left untreated, blastomycosis gradually leads to death. When treated, however, patients begin to improve within one week and, with intensive treatment, may be cured within several weeks. The highest rate of recovery is among patients who only have skin lesions. People with the disseminated form of the disease are least likely to be cured and most likely to suffer a relapse.

Because the fungus that causes blastomycosis is airborne and microscopic, theonly form of prevention is to avoid visiting areas where it is found in thesoil. For many people this is impractical. Since the disease is rare, peoplewho maintain general good health do not need to worry much about infection.

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