Langerhans cell histiocytosis

Characterized by the clonal proliferation of pathogenic Langerhans cells in single or multiple organs.

Exact etiology and pathogenesis is unknown; however, it is thought to be either a malignant process or due to immune dysregulation.

Clinical presentation is heterogeneous and ranges from self-healing bone lesions to multisystem, life-threatening disease.

Tissue biopsy of lesional cells showing the presence of CD1a and langerin (CD207) is definitive for diagnosis in the correct clinical setting.

Multisystem disease is treated with systemic, multiagent chemotherapy.

Treatment of relapsed disease and CNS neurodegenerative disease remains a challenge.

Prognostic factors include rapid response to therapy and risk-organ involvement.

Langerhans cell histiocytosis (LCH) is a rare disease characterized by the clonal proliferation of pathogenic Langerhans cells and cytokine over-production. This leads to inflammation and tissue destruction in different organs of the body. [1] Nezelof C, Basset F, Rousseau MF. Histiocytosis X histogenetic arguments for a Langerhans cell origin. Biomedicine. 1973;18:365-371. http://www.ncbi.nlm.nih.gov/pubmed/4356601?tool=bestpractice.com [2] Arceci RJ, Longley BJ, Emanuel PD. Atypical cellular disorders. Hematology Am Soc Hematol Educ Program. 2002;297-314. http://www.ncbi.nlm.nih.gov/pubmed/12446429?tool=bestpractice.com It may affect either a single organ system or multiple organs, and commonly involves the bone, skin, lungs, liver, spleen, bone marrow, pituitary gland, and eyes. Less common sites involved include the lymph nodes, thyroid, ears, CNS, gastrointestinal system, and oral mucosa. [3] Histiocyte Society. Langerhans cell histiocytosis: Histiocyte Society evaluation and treatment guidelines. April 2009. http://www.histiocytesociety.org (last accessed 28 September 2017). http://www.histiocytesociety.org/document.doc?id=290 [4] Broadbent V, Gadner H. Current therapy for Langerhans cell histiocytosis. Hematol Oncol Clin North Am. 1998;12:327-338. http://www.ncbi.nlm.nih.gov/pubmed/9561903?tool=bestpractice.com Because pathologic Langerhans cells (dendritic cells found in the skin) are the cell type common to the various manifestations of the disease, the term "LCH" is preferred over previous names such as "histiocytosis X." [1] Nezelof C, Basset F, Rousseau MF. Histiocytosis X histogenetic arguments for a Langerhans cell origin. Biomedicine. 1973;18:365-371. http://www.ncbi.nlm.nih.gov/pubmed/4356601?tool=bestpractice.com [2] Arceci RJ, Longley BJ, Emanuel PD. Atypical cellular disorders. Hematology Am Soc Hematol Educ Program. 2002;297-314. http://www.ncbi.nlm.nih.gov/pubmed/12446429?tool=bestpractice.com It is the most common type of histiocytosis (i.e., syndrome characterized by the abnormal proliferation of histiocytes). [5] Weitzman S, Egeler RM. Histiocytic disorders of children and adults: introduction to the problem, overview, historical perspective and epidemiology (adapted from Favara BE, et al. Med Pediatr Oncol 1997). In: Weitzman S, Egeler RM, eds. Histiocytic disorders of children and adults. Cambridge, UK: Cambridge University Press; 2005:3.