Langerhans Cell Histiocytosis
Pronunciation: LANG-er-hanz sel his-tee-oh-sy-TOH-sis
Also written as: LCH — Langerhans Cell Histiocytosis
A clonal proliferative disorder of Langerhans cells characterised by the accumulation of CD1a- and CD207 (langerin)-positive histiocytes in various tissues, ranging from isolated bone lesions to multisystem disease.
Full Definition
Langerhans cell histiocytosis (LCH) is a neoplastic disorder caused by clonal proliferation of cells bearing the phenotype of Langerhans cells, now recognized as a myeloid neoplasm driven in the majority of cases by the BRAF V600E mutation. It encompasses a wide clinical spectrum: unifocal (single-system, single-site) disease such as eosinophilic granuloma of bone, multifocal single-system disease, and multisystem disease that may involve bone, skin, pituitary, lung, liver, and haematopoietic system. In pediatric pathology reports, confirmation requires immunohistochemical positivity for CD1a and CD207 (langerin) and the presence of Birbeck granules on electron microscopy. Editors should be aware that 'histiocytosis X,' 'eosinophilic granuloma,' 'Hand–Schüller–Christian disease,' and 'Letterer–Siwe disease' are all obsolete designations now unified under LCH. The acronym LCH is standard after first-use expansion.
Usage
Usage note: Obsolete synonyms (histiocytosis X, eosinophilic granuloma, Letterer–Siwe disease, Hand–Schüller–Christian disease) should be replaced with 'Langerhans cell histiocytosis' on first use, with the deprecated term given in parentheses if historically relevant.
In Context
- "The skull biopsy showed sheets of CD1a-positive cells with grooved nuclei, consistent with Langerhans cell histiocytosis." — Pediatric pathology report
- "Editors should flag use of the term 'histiocytosis X' as it has been superseded by 'Langerhans cell histiocytosis' in all current classification systems." — Journal style guide note