hematology and oncology
Langerhans Cell Histiocytosis
Introduction
Langerhans cell histiocytosis (LCH) is a proliferation of dendritic mononuclear cells with infiltration into organs locally or diffusely. Most cases occur in children. Manifestations may include lung infiltrates; bone lesions; rashes; and hepatic, hematopoietic, and endocrine dysfunction. Diagnosis is based on biopsy. Factors predicting a poor prognosis include age<2 years and dissemination, particularly involving the hematopoietic system, liver, spleen, or a combination. Treatments include supportive measures and chemotherapy or local treatment with surgery or radiation therapy as indicated by the extent of disease. (See also Pulmonary Langerhans Cell Histiocytosis .) Langerhans cell histiocytosis (LCH) is a dendritic cell (antigen-presenting cell) disorder. It can cause distinct clinical syndromes that have been historically described as eosinophilic granuloma, Hand-Schüller-Christian disease, and Letterer-Siwe disease. Because these syndromes may be varied manifestations of the same underlying disorder and because most patients with LCH have manifestations of more than one of these syndromes, the designations of the separate syndromes (except for eosinophilic granuloma) are now mostly of historical significance. Estimates of the prevalence of LCH vary widely (eg, from about 1:50,000 to 1:200,000). Incidence is 5 to 8 cases/million children. All patients with LCH have evidence of activation of the RAS-RAF-MEK-ERK signaling pathway ( General reference ). In LCH, abnormally proliferating dendritic cells infiltrate one or more organs. Bones, skin, teeth, gingival tissue, ears, endocrine organs, lungs, liver, spleen, lymph nodes, and bone marrow may be involved. Organs may be affected by infiltration, causing dysfunction, or by compression from adjacent enlarged structures. In about half of patients, more than one organ is involved. 