Colonic ulceration in histiocytosis X.

Gastrointestinal symptoms in histiocytosis X are distinctly unusual. This report describes a 5-month-old infant with a prolonged history of lower gastrointestinal bleeding which was found to be caused by diffuse histiocytic infiltration of the colon. Immunopathologic and electron microscopic studies confirmed the diagnosis of histiocytosis X. The differential diagnosis of lower gastrointestinal bleeding in young children should include histiocytosis X.