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Blastomycosis

Blastomycosis

Definition

Blastomycosis is an infection caused by inhaling microscopic particles (spores) produced by the fungus Blastomyces dermatitidis. Blastomycosis may be 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 (systemic).

Description

Blastomycosis is a fungal infection caused by Blastomyces dermatitidis. 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 southeastern United States, the Mississippi River valley, southern Canada, and Central America. Blastomycosis is also called Gilchrist's disease, Chicago disease, or North American blastomycosis. Another South and Central American disease, paracoccidioidomycosis, is sometimes called South American blastomycosis, but despite the similar name, this disease is substantially different from North American blastomycosis. Canine blastomycosis, a common dog disease, is caused 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 more often infect 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.

Causes and symptoms

Once inhaled, the spores of B. dermatitidis can lodge in the lungs and cause a localized inflammation. This is known as primary pulmonary blastomycosis. The disease does not spread from one person to another. In the early stages, symptoms may include a dry cough, fever, heavy sweating, fatigue, and a general feeling of ill health. In approximately 25% of blastomycosis cases, only the lungs 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 form small cavities.

In another 35%, 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 do not heal. Approximately 19% of infected people have skin sores without infection in the lungs.

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

Diagnosis

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 or skin. 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 look on the x ray. Because its symptoms vary widely, blastomycosis is often misdiagnosed.

KEY TERMS

Abscess An area of inflamed and injured body tissue that fills with pus.

Acidophilus The bacteria called Lactobacillus acidophilus that is usually found in yogurt.

Alveoli Small air pockets in the lungs that increase the surface area for oxygen absorption.

Bifidobacteria A group of bacteria normally present in the intestine. Commercial supplements containing these bacteria are available.

Biopsy The removal of a tissue sample for diagnostic purposes.

Immunocompromised A state in which the immune system is suppressed or not functioning properly.

Spores The small, thick-walled reproductive structures of fungi.

Sputum Mucus and other matter coughed up from airways.

Systemic Not localized to a single area of the body but, instead, involving one or more body systems.

Treatment

Blastomycosis must be treated or it will gradually lead to death. Treatment with the fungicidal drug ketoconazole (Nizoral) taken orally is effective in about 75% of patients. 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 receive other drugs to minimize the its side effects.

Alternative treatment

Alternative treatment for fungal infections focuses on creating an internal environment where the fungus cannot survive. This is accomplished by eating a diet low in dairy products, sugars, including honey and fruit juice, and foods like beer that contain yeast. This is complemented by a diet consisting, in large part, of uncooked and unprocessed foods. Supplements of vitamins C, E, A-plus, and B complex may also be useful. Lactobacillus acidophilus and Bifidobacterium will replenish the good bacteria in the intestines. Some antifungal herbs, like garlic (Allium sativum ), can be consumed in relatively large doses and for an extended period of time in order to increase effectiveness. A variety of antifungal herbs, such as myrrh (Commiphora molmol ), tea tree oil (Melaleuca spp.), citrus seed extract, pau d'arco tea (Tabebuia impetiginosa ), and garlic may also be applied directly to the infected skin.

Prognosis

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 and most likely to suffer a relapse.

Prevention

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

Resources

ORGANIZATIONS

National Organization for Rare Disorders. P.O. Box 8923, New Fairfield, CT 06812-8923. (800) 999-6673. http://www.rarediseases.org.

OTHER

"Blastomycosis." Vanderbilt University Medical Center. http://www.mc.vanterbilt.edu/peds/pid/infect/blastomy.html.

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blastomycosis

blastomycosis (blast-oh-my-koh-sis) n. any disease caused by parasitic fungi of the genus Blastomyces, which may affect the skin (forming wartlike ulcers and tumours) or involve various internal tissues.

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blastomycosis

blastomycosis: see fungal infection.

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Blastomycosis

Blastomycosis

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

BIBLIOGRAPHY

Introduction

Blastomycosis is a rare fungal infection caused by inhaling the fungal organism Blastomyces dermatitidis through the nose or mouth. The organism is usually found in habitats containing wood and soil. It lives commonly as a mold in warm, sandy soils located near water and within moist soil full of decomposing organic matter. The infection is restricted to humans, dogs, and other mammals in portions of North America. Human symptoms of the infection are similar to the influenzalike disease of the lungs called histoplasmosis (also called Darling's disease). Rarely, persons with blastomycosis develop chronic pulmonary infection or widespread disseminated infection.

When found in a host, Blastomyces dermatitidis lives as yeast. Because it lives as mold outside a host and as yeast inside, it is called a biphasic organism. Blastomycosis is commonly misdiagnosed as Valley fever (coccidioidomycosis), Lyme disease, or other viral infections.

Disease History, Characteristics, and Transmission

The first description of blastomycosis came in 1876 from French biologist Philippe Edouard Leon Van Tieghem (1839–1914). Later, in 1894, American dermatologist Thomas Gilchrist (1862–1927), from the University of Maryland School of Medicine, described it more thoroughly. At that time, Gilchrist isolated and proved the cause of the human infection. Because of this description, it is often called Gilchrist's disease or Gilchrist's mycosis. It is also sometimes called Chicago disease and North American blastomycosis.

Transmission of the fungus is by inhalation of airborne spores after contaminated soil has been disturbed. Persons, such as forestry workers, campers, hunters, and farmers, located near wooded sites are at increased risk. People who have compromised immune systems also are at high risk.

According to the Centers of Disease Control and Prevention Division of Bacterial and Mycotic Diseases, symptoms occur in about 50% of all cases. Common symptoms, which sometimes parallel symptoms of influenza (flu), include a nonproductive cough, fever, chills, headache, and pain or stiffness in muscles or joints. When it resembles bacterial pneumonia, symptoms include high fever, chills, a productive cough with brown or bloody-looking sputum, and chest pain of the lungs. When it looks like tuberculosis or lung cancer, symptoms include a low-grade fever, productive cough, night sweats, and weight loss. Other symptoms can include shortness of breath, sweating, tiredness, overall discomfort and ill-feeling, rash, skin and bone lesions, and problems with the bladder, kidney, prostate, and testes.

WORDS TO KNOW

HOST: Organism that serves as the habitat for a parasite, or possibly for a symbiont. A host may provide nutrition to the parasite or symbiont, or simply a place in which to live.

MYCOTIC DISEASE: Mycotic disease is a disease caused by fungal infection.

SPORE: A dormant form assumed by some bacteria, such as anthrax, that enable the bacterium to survive high temperatures, dryness, and lack of nourishment for long periods of time. Under proper conditions, the spore may revert to the actively multiplying form of the bacteria.

Once the infection is inside the lungs, it grows rapidly, becoming noticeable in the blood, brain, bone, lymphatic system, skin, and genital and urinary systems. The incubation period is generally 30 to 100 days. No symptoms occur in about half the infections. The death rate from the infection is about 5%.

Scope and Distribution

Blastomycosis is concentrated in parts of North America, especially in the central southern, midwestern, and southeastern parts of the United States and the northwestern part of Ontario in Canada. Infection is more frequent in the basin areas around the Ohio River and Mississippi River and in the areas surrounding the Great Lakes. It occurs in about one to two people out of 100,000 in these North American regions.

Some cases are reported in Central America, South America, and Africa. Although anyone can contract the infection, it more commonly affects people with compromised immune systems. Males are more likely to become infected than are females.

Treatment and Prevention

Once identified, the diagnosis can be confirmed with cellular and tissue tests such as the KOH test. The KOH test is a procedure performed with a microscope that uses potassium hydroxide (KOH) to dissolve skin tissue and reveal fungal cells. Other diagnostic tests employed may include chest x-rays to show nodule growth or pneumonia; skin, organ or tissue biopsies; and blood and sputum cultures. When other tests fail, a urine antigen test usually identifies the disease.

Blastomycosis in the lungs does not always require drug treatment to eliminate it. However, when the infection spreads outside the lungs or has become severe within the lungs, amphotericin B (such as Abelcet® and Fungisome®), itraconazole (such as Sporanox®), or other antifungal medicines may be prescribed orally or intravenously. Amphotericin B is usually reserved for severe cases. While it is more effective than other antifungals, it also is more toxic. Periodic follow-up by a physician is recommended to detect any recurrences. Cure rates are high, however, treatment often takes many weeks or months.

People with minor irritations of the skin and lungs usually recover without suffering permanent problems. Major complications—such as large abscesses, relapses, or recurrences of the disease and negative side effects of drugs—can lead to complications. If patients do not recover, they may develop chronic lung infection or widespread infection of the bones, skin, and genitourinary tract. On occasion, the fungus affects the meninges, the protective covering of the brain and spinal column. If left untreated, severe cases can progress rapidly and eventually cause death.

Impacts and Issues

Blastomycosis has not been accurately and reliably reported by the medical community in the past. This is largely due to the fact that national reporting is not required in Canada and the United States and that its occurrence has been restricted to North America. However, the disease is becoming better defined as more research is performed. Unfortunately it is still not completely understood. Lack of information about the disease is primarily due to the difficulty in isolating the causative organism from its natural environment.

Most medical practitioners consider blastomycosis to be an important mycotic disease (fungal disease or infection). According to the Canadian Medical Association Journal (CMAJ), its prevalence (or endemicity) may be more extensive than previously thought. The CMAJ suggests that physicians include it in the potential diagnoses of unexplained granulomatous pulmonary (relating to the lungs) disease and cutaneous (relating to the skin) disease.

Currently, a number of uncertainties still surround the origins, characteristics, causes, and other important medical facts (that is, the epidemiology) of blastomycosis. A greater understanding of the epidemiology of this disease will allow it to be more effectively combated in the future.

See AlsoCoccidioidomycosis; Histoplasmosis; Mycotic Disease.

BIBLIOGRAPHY

Books

Al-Doory, Yousef, and Arthur F. DiSalvo, eds. Blastomycosis. New York: Plenum, 1992.

Korting, H. C., ed. Mycoses: Diagnosis, Therapy and Prophylaxis of Fungal Diseases. Berlin, Germany: Blackwell Science, 2005.

Sobel, Jack D. Contemporary Diagnosis and Management of Fungal Infections. Newtown, PA: Handbooks in Health Care, 2003.

Periodicals

Lester, Robert S., et al. “Novel Cases of Blastomycosis Acquired in Toronto, Ontario.” Canadian Medical Association Journal 163 (November 14, 2000): 1309–1312.

Ross, John J., and Douglas N. Keeling. “Cutaneous Blastomycosis in New Brunswick: Case Report.” Canadian Medical Association Journal 163 (November 14, 2000): 1303–1305.

Web Sites

Canadian Medical Association. “Blastomycosis.” November 4, 2000. <http://www.cmaj.ca/cgi/content/full/163/10/1231> (accessed March 11, 2007).

Centers of Disease Control and Prevention. “Blastomycosis.” October 6, 2005. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/blastomycosis_t.htm> (accessed March 11, 2007).

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