In histiocytosis, also called Langerhans' cell histiocytosis or eosinophilic granuloma, there are too many of a type of cell called histiocytes or macrophages in the tissues. This disease affects the soft tissues and the bones and can also affect the endocrine system.

This rare disease can be difficult to diagnose. It has different forms, and can be different in children and adults. If you have histiocytosis, you may have damaged areas called lesions in your bones, mouth and gums or skin. Doctors might use chemotherapy or low doses of radiation therapy to treat skin or bone lesions. You might also have surgery to treat or prevent complications from this disease.