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.
Causes, incidence, and risk factors
Blastomycosis is a rare fungal infection. It is most common in the central and southeastern United States, and in Canada, India, Israel, Saudi Arabia, and Africa. A person gets infected by inhaling fungal particles that are found in moist soil, particularly 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, infecting them. In some people, the fungus then spreads (disseminates) to other areas of the body. The infection may affect the skin, bones and joints, genitourinary tract, and other systems. Skin symptoms are a sign of widespread (disseminated) blastomycosis.
Skin symptoms occur in about 80% of people whose blastomycosis infection spreads beyond their lung.
Over time, these skin lesions can lead to scarring and loss of skin color (pigment).
Signs and tests
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 form and stage of the disease.
What happens depends on the form of blastomycosis and the individual's immune system. In immunosuppressed individuals, long-term treatment may be required to prevent symptoms from coming back.
Abscesses (pockets of pus)
Additional (secondary) skin infection caused by bacteria
Complications related to medications (for instance, amphotericin B can have severely unpleasant side effects)
Spontaneously draining nodules
Calling your health care provider
Some of the skin problems caused by blastomycosis can be similar to skin problems caused by other illnesses. Tell your doctor if you develop any worrisome skin problems.
Kauffman CA. Blastomycosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 355.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.