Definition of Histiocytosis

Histiocytosis: One of several disorders in which histiocytes start to multiply and proliferate abnormally. The result can be tissue damage, pain, the development of tumor-like lumps, fatigue, and other symptoms. If histiocytosis affects the pituitary gland, diabetes insipidus may also develop. Treatment includes radiation and chemotherapy, although for reasons unknown, some cases of histiocytosis go into remission without treatment.