A usually fatal disease, most common in infants, caused by the overproduction of a specialised type of immune cell.
The most common of three distinct histiocytosis syndromes collectively known as Langerhans cell histiocytosis, marked by proliferation of histiocytes in the viscera, bones, and skin. It is believed that this disease and the other two forms — eosinophilic granuloma of bone and Hand-Schiiller-Christian syndrome — share a common pattern of granulomatous lesions with histiocyte proliferation.