Langerhans cell histiocytosis(LCH) is a rare disease involving clonal proliferation of Langerhans cells, abnormal cells deriving from bone marrow and capable of migrating from skin to lymph nodes. Clinically, its manifestations range from isolated bone lesions to multisystem disease. LCH is part of a group of clinical syndromes called histiocytoses, which are characterized by an abnormal proliferation of histiocytes (an archaic term for activated dendritic cells and macrophages). These diseases are related to other forms of abnormal proliferation of white blood cells, such as leukaemias and lymphomas.

The disease has gone by several names, including Hand–Schüller–Christian disease, Abt-Letterer-Siwe disease, and histiocytosis X, until it was renamed in 1985 by the Histiocyte Society.

Acknowledgement: Dott.ssa Sandra Pennacchini