A skin lesion of blastomycosis is a symptom of an infection with the fungus Blastomyces dermatitidis. The skin becomes infected as the fungus spreads throughout the body. Another form of blastomycosis is only on the skin and usually gets better on its own with time. This article deals with the more widespread form of the infection.
Blastomycosis is a rare fungal infection. It is most often found in:
- Canada, around the Great Lakes
- South central and north central United States
- Saudi Arabia
A person gets infected by breathing in particles of the fungus that are found in moist soil, especially where there is rotting vegetation. People with immune system disorders are at highest risk for this infection.
The fungus enters the body through the lungs and infects them. In some people, the fungus then spreads (disseminates) to other areas of the body. The infection may affect the skin, bones and joints, genitals and urinary tract, and other systems. Skin symptoms are a sign of widespread (disseminated) blastomycosis.
In many people, skin symptoms develop when the infection spreads beyond their lungs.
- They may look like warts or ulcers.
- They are usually painless.
- They may vary from gray to violet in color.
The pustules may:
- Form ulcers
- Bleed easily
- Occur in the nose or mouth
Over time, these skin lesions can lead to scarring and loss of skin color (pigment).
Exams and Tests
The health care provider will examine your skin and ask about symptoms.
The infection is diagnosed by identifying the fungus in a culture taken from a skin lesion. This usually requires a skin biopsy.
This infection is treated with antifungal drugs such as amphotericin B, itraconazole, ketoconazole, or fluconazole. Either oral or intravenous (directly in the vein) drugs are used, depending on the drug and stage of the disease.
What happens depends on the form of blastomycosis and the person's immune system. People with a suppressed immune system may need long-term treatment to prevent symptoms from coming back.
Complications may include:
- Abscesses (pockets of pus)
- Another (secondary) skin infection caused by bacteria
- Complications related to medicines (for instance, amphotericin B can have severe side effects)
- Spontaneously draining nodules
- Severe body-wide infection and death
When to Contact a Medical Professional
Some of the skin problems caused by blastomycosis can be similar to skin problems caused by other illnesses. Tell your provider if you develop any worrisome skin problems.
Bradsher RW. Blastomycosis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 266.
Kauffman CA. Blastomycosis. In: Goldman L, Shafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 334.
Review Date 10/24/2016
Updated by: David L. Swanson, MD, Vice Chair of Medical Dermatology, Associate Professor of Dermatology, Mayo Medical School, Scottsdale, AZ. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.