Natural history of histiocytosis-X.

Histiocytosis-X can involve many organs and tissues in all age groups and in both sexes and occurs most often in caucasians. The signs and symptoms observed in the patient are directly related to the infiltration of Langerhans histiocytes, which compress or displace normal tissues and cause destruction of the tissues and organs involved. The disease tends to be benign and self-limiting when the involvement is limited to only one site. When more than one site is involved, the disease course can be chronic or acute. The chronic course tends to smolder for years, causing significant morbidity and disability but not death. The acute form tends to cause significant morbidity and early mortality.