Langerhans cell histiocytosis
Definition: a set of closely related disorders unified by a common proliferating element, the Langerhans cell. Three overlapping clinical syndromes are recognized: a single site disease (eosinophilic granuloma), a multifocal unisystem process (Hand-Schuller-Christian syndrome), and a multifocal, multisystem histiocytosis (Letter-Siwe syndrome.) Formerly this process was known as histiocytosis X.
Synonym(s): histiocytosis X