Causes

Histoplasmosis is a fungal infection. It occurs throughout the world. In the United States, it is most common in the southeastern, mid-Atlantic, and central states.

Histoplasma fungus grows in soil. When particles become airborne, they can be breathed into the lungs, causing infection. Soil contaminated with bird or bat droppings may have a higher concentration of the fungus.

After infecting the lungs, the fungus travels to distant areas of the body, including the skin. This is a sign of widespread (disseminated) infection. Skin lesions can be caused by an immune response to the infection (usually a rash called erythema nodosum or erythema multiforme), or by the fungus itself when it spreads to the skin.

Widespread infection is most common in immunosuppressed people, such as those with AIDS or cancer, or those who have had a transplant.

Symptoms

The symptoms may include:

• Mouth ulcer, usually painless
• Pustules or nodules all over the body
• Red spots on the skin (erythema nodosum)
• Red lumps on the skin (erythema multiforme), usually on the lower legs

Exams and Tests

In some cases, a biopsy of the skin lesion can identify the fungus. Rashes due to erythema nodosum and erythema multiforme, however, usually do not have fungus in them. Blood and urine tests may help detect the fungus in some cases.

Treatment

Antifungal drugs, such as amphotericin B, itraconazole, and ketoconazole, are the usual treatments. Antifungals may be given intravenously depending on the form or stage of disease. In some cases, long-term treatment with antifungal drugs may be needed.

Outlook (Prognosis)

The outlook depends on the form of histoplasmosis and the condition of the individual's immune system. Death can occur in some cases.

Possible Complications

• Bacterial skin infection
• Complications of medications (for example, amphotericin B can have severe, unpleasant side effects)

When to Contact a Medical Professional

The skin lesions may be similar to skin problems from other infections or illnesses. Notify your health care provider if you develop any suspicious lesions on your skin, so that you may be tested correctly.

Prevention

Histoplasmosis may be prevented by reducing exposure to dust in chicken coops, bat caves, and other high-risk locations. Wear masks and other protective equipment if you work in these environments.

References

Kauffman CA. Histoplasmosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 353.

Updated: 4/15/2012

Reviewed by: 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, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.