Histoplasmosis is a widespread fungal infection that occurs worldwide. The infection gets into the body through the lungs. Histoplasma grows in soil. The fungal particles become airborne, and are breathed in. Soil contaminated with bird or bat droppings may have a higher concentration of mold. The skin lesions can be caused by an immune reaction to the lung infection. In this case, lesions called erythema nodosum or erythema multiforme occur. Skin lesions can also occur when the fungus has spread to distant organs throughout the body, including the skin, bone marrow, and the brain. This is most common among immunosuppressed people, such as those with AIDS.
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