CD1A and Langerhans cell histiocytosis: Langerhans cell histiocytosis (LCH) is a rare hematopoietic disorder of unknown pathogenesis characterized by abnormal proliferation of CD1a-positive dendritic cells, which leads to a variety of clinical manifestations.[1] LCH mostly occurs in children, it is considered to be extremely rare in adults with an incidence of 1 to 2 cases every million.[1] LCH may occur in a single organ or multisystem organ diseases, those with multisystem involvement usually have a poor prognosis.