Langerhans cell histiocytosis: an update

The histiocytoses represent a heterogeneous group of disorders that are characterized by the proliferation and accumulation of reactive or neoplastic histiocytes within various tissues. Langerhans cell histiocytosis (LCH) is the commonest of these disorders and it is associated with high morbidity and mortality, especially in children. LCH is a poorly understood disease with features suggestive of a neoplastic, reactive, or immune dysregulation process. The clinical spectrum of LCH is considered to be broad and includes from self-resolving involvement of a single organ to a potentially fatal multisystem disease. The purpose of this review is to undertake an update of LCH with emphasis on the current recommendations regarding the classification, evaluation and treatment of this enigmatic disease.