A rare occurrence of Langerhans cell histiocytosis in an adult.

Langerhans Cell Histiocytosis (LCH) is a disease process characterized by accumulation and infiltration of cells, showing ultrastructural and immunohistochemical similarities to Langerhans' cell, in the affected tissues. It exhibits extreme clinical heterogeneity. LCH was historically divided into 3 clinical entities based on extent of tissue involvement and severity of presentation. These 3 entities were eosinophilic granuloma, Hand-Schuler-Christian disease, Letterer-Siwe disease. Owing to similarities of their histologic appearance, they were grouped together under the term histiocytosis X. It was recently changed to LCH, emphasizing the primary cell involved in the disease process. LCH is a rare disease with an incidenceestimated to be 4.0 to 5.4 per million population. Males are affected twice as frequently as females. The disease may occur at any age with peak incidence in children aged 1 to 3 years. We describe an unusual case of a 65-year-old man who presented with painless swelling in anterior region of mandible.