Histoplasmosis and erythema nodosum

Histoplasmosis is an infection caused by a fungus found in soil contaminated with bird or bat droppings. In some people, the immune response to the infection is accompanied by erythema nodosum: tender, deep lumps under the skin, commonly over the shins. The nodules are an inflammatory skin reaction rather than fungal growth in the lump itself. They may change from red to darker shades as they settle and can occur with fever, fatigue, cough, chest discomfort, or joint aches.

Arrange medical assessment if painful shin nodules appear with a recent respiratory illness, exposure to disturbed soil, or symptoms affecting the chest or joints. Tell the clinician about travel, work, construction or excavation, and contact with bird or bat habitats. Evaluation may include a skin examination, a review of symptoms, and tests chosen to look for infection or other inflammatory causes. Rest, leg elevation, and clinician-approved pain relief may help while the cause is clarified. Treatment is directed at the underlying problem; oral corticosteroids need specialist guidance.

Seek urgent care for severe breathing difficulty, chest pain, confusion, fainting, coughing blood, or rapidly worsening illness. Arrange prompt review for persistent fever, worsening cough, marked weakness, spreading painful nodules, or difficulty walking. Do not assume every shin lump is erythema nodosum: infection, medication reactions, and other inflammatory conditions can look similar.

Ask whether your skin findings fit erythema nodosum, what evidence supports histoplasmosis, and which tests are appropriate. Ask whether you need treatment for an active infection, how to manage pain, which symptoms should trigger urgent care, and whether follow-up is needed as the nodules change.