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 higher risk for this infection, though healthy people can also develop this disease.
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, voriconazole, or fluconazole. Either oral or intravenous (directly in the vein) drugs are used, depending on the drug and stage of the disease.
How well you do depends on the form of blastomycosis and on your 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.
Embil JM, Vinh DC. Blastomycosis. In: Kellerman RD, Rakel DP, eds. Conn's Current Therapy 2022. Philadelphia, PA: Elsevier; 2022:872-876.
Gauthier GM, Klein BS. Blastomycosis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 264.
Kauffman CA, Galgiani JN, R George T. Endemic mycoses. In: Goldman L, Shafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 316.
Review Date 11/18/2022
Updated by: Elika Hoss, MD, Assistant Professor of Dermatology, Mayo Clinic, Scottsdale, AZ. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.