<unk>  <unk>  is an abnormal clonal proliferation of Langerhans cells, abnormal cells deriving from bone marrow and capable of migrating from skin to lymph nodes. Symptoms range from isolated bone lesions to multisystem disease.<unk>  is part of a group of 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 leukemias and lymphomas. The disease has gone by several names, including Hand–Schüller–Christian disease, Abt-Letterer-Siwe disease, Hashimoto-Pritzker disease (a very rare self-limiting variant seen at birth) and histiocytosis X, until it was renamed in 1985 by the Histiocyte Society.
Langerhans cell histiocytosis
X-type histiocytosis
Sea-blue histiocytosis
Malignant histiocytosis
Crystal-storing histiocytosis
Non-X histiocytosis
Progressive nodular histiocytosis
Langerhans cell sarcoma