Langerhans Cell Histiocytosis

Definition

Langerhans cell histiocytosis (LCH) is a rare disease involving clonal proliferation of Langerhans cells (Cotran 2005, Halpern 1997). These abnormal Langerhans cells area derived from bone marrow and capable of migrating to either skin or lymph nodes. LCH is a part of clinical syndromes referred to as histiocytoses, which are characterized by an abnormal proliferation of histiocytes (or activated dendritic cells and macrophages). There are three classes of histiocytoses: Langerhans cell histiocytosis (Class I), non-Langerhans cell histiocytosis (Class II), and malignant histiocytosis (Class III). LCH was previously called histiocytosis X, but was renamed in 1985 (Cotran 2005, Halpern 1997, Satter 2008).

Etiology

Langerhans cells are dendritic cells containing large Birbeck granules found in the epidermis, lymph nodes, and other organs. During infection of an area of skin, Langerhans cells process microbial antigens and become fully-functional MHC class II antigen presenting...