Merck Manual

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(Gilchrist Disease; North American Blastomycosis)


Sanjay G. Revankar

, MD, Wayne State University School of Medicine

Reviewed/Revised Apr 2021 | Modified Sep 2022
Topic Resources

Blastomycosis is an infection, mainly of the lungs, caused by the fungus Blastomyces dermatitidis.

  • People have a fever, chills, and drenching sweats and sometimes chest pain, difficulty breathing, and a cough.

  • The infection may spread to the skin, bones, reproductive and urinary tracts, and tissues covering the brain, causing swelling, pain, and other symptoms.

  • A sample of infected sputum or tissues is removed and sent for culture, and a chest x-ray is taken.

  • Antifungal drugs must be taken for months.

Spores of Blastomyces enter the body through the airways when the spores are inhaled. Thus, blastomycosis affects primarily the lungs, but the fungi occasionally spread through the bloodstream to other areas of the body, most commonly the skin. It can also spread to the prostate gland, epididymides, testes, seminal vesicles, kidneys, vertebrae, ends of long bones, the deepest layer of the skin, central nervous system, the membranes lining the mouth or nose, thyroid gland, lymph nodes, and bone marrow.

Blastomycosis can occur in people who have a normal immune system. However, it may be more common among and more severe in some people with a weakened immune system. Unlike most fungal infections, blastomycosis is not more common among people with AIDS. However, it tends to be more severe in people with AIDS.

Most cases of blastomycosis occur in areas of North America where the fungus lives in the soil near river beds:

  • The Ohio and Mississippi River valleys (extending into the middle Atlantic and southeastern states)

  • The northern Midwest

  • Upstate New York

  • Areas of southern Canada that border the Great Lakes and Saint Lawrence River

Rarely, the infection occurs in the Middle East and Africa.

Symptoms of Blastomycosis

Sometimes blastomycosis of the lungs causes no symptoms or causes symptoms that disappear quickly and are not recognized.

When symptoms do occur, they can begin abruptly or gradually. They include a fever, chills, and drenching sweats. Chest pain, difficulty breathing, and a hacking cough that may or may not bring up sputum may also develop. The lung infection usually progresses slowly, but people sometimes get better without treatment. In some people, infection progresses rapidly.

When blastomycosis spreads from the lungs, it can affect many areas of the body, but the most common sites are the following:

  • Skin

  • Bones

  • Reproductive and urinary tracts (including the prostate gland)

  • Brain and the tissues that cover it

Skin infection begins as very small, raised bumps (papules), which may contain pus. Raised, warty patches then develop, surrounded by tiny, painless collections of pus (abscesses).

Tissues over infected bones may become swollen, warm, and painful.

In men, the coiled tube on top of a testis (epididymis) may swell, causing pain, or infection of the prostate gland (prostatitis) may cause discomfort.

Fungi can spread to the tissues that cover the brain and spinal cord (meninges), causing fungal meningitis. Abscesses Abscess of the Brain A brain abscess is a pocket of pus in the brain. An abscess may form in the brain when bacteria from an infection elsewhere in the head or in the bloodstream or from a wound enter the brain... read more may develop in the brain. This infection can cause headache and confusion.

Diagnosis of Blastomycosis

  • Examination and culture of a sample of infected material

  • Chest x-ray

A doctor diagnoses blastomycosis by sending a sample of sputum or infected tissue to a laboratory to be examined under a microscope and cultured. A chest x-ray is taken to check for signs of infection in the lungs.

Doctors may also test a urine sample for proteins (antigens Overview of the Immune System ) released by the fungus.

Treatment of Blastomycosis

  • Antifungal drugs

Blastomycosis, if severe, is treated with amphotericin B, given intravenously. If blastomycosis is mild to moderate, itraconazole is given by mouth.

With treatment, people begin to feel better fairly quickly, but the drugs must be continued for 6 to 12 months or sometimes longer. Without treatment, blastomycosis slowly worsens and, rarely, leads to death.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Amphocin, Fungizone
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