A manifestation of histoplasmosis , produced either by an imune reaction to localized infection or disseminated (widespread) disease caused by the fungus Histoplasma capsulatum .
Causes, incidence, and risk factors
Histoplasmosis is a widespread fungal infection which occurs worldwide. In the US, it is most common in the southeastern, mid-Atlantic, and central states. The lungs are the portal of entry for this infection. Histoplasma grows as a mold in soil, and infection results from inhalation of airborne fungal particles. Soil contaminated with bird or bat droppings may have a higher concentration of mold. The skin lesions of histoplasmosis are varied and can be caused by an immune reaction to acute pulmonary (lung) involvement. In this case, lesions called erythema nodosum or erythema multiforme (target lesions) occur. Skin lesions can also be a manifestation of disseminated histoplasmosis, where the fungus has spread to distant organs throughout the body including the skin, the bone marrow and the brain amongst others. Disseminated histoplasmosis is most common amongst immunosuppressed people, such as those with AIDS.
Signs and tests
If the skin lesion is seen in the setting of disseminated histoplasmosis, a biopsy of the skin lesion may show the associated fungus. Other findings such as erythema nodosum and erythema multiforme are manifestations of the body's inflammatory reaction and usually do not have fungus in them.
Treatment
The mainstay of treatment includes antifungal agents such as amphotericin B, itraconazole, and ketoconazole. Antifungals may be given intravenously depending on the form or stage of disease. In individuals with disseminated disease, long-term suppression with oral antifungal agents may be used.
Expectations (prognosis)
Prognosis depends on the clinical form of histoplasmosis and the immune system status of the individual. The death rate is highest in disseminated histoplasmosis.
Calling your health care provider
The skin manifestations of histoplasmosis are varied and may be similar to skin findings seen in other infections or illnesses. Notify your health care provider if you develop any suspicious lesions on your skin so that you may be appropriately evaluated.
Prevention
Prevention of histoplasmosis involves minimizing exposure to dust in contaminated environments -- such as chicken coops and bat caves. Wear protective equipment such as masks if you work in these environments.