[Adult Langerhans cell histiocytosis].
Langerhans cell histiocytosis (LCH) is a rare disease affecting both genders and can occur at any age. It often evolves through successive flares, and its severity varies from benign forms that don't require treatment to life threatening disease. Some patients have important functional impairment with psychological and social consequences and prolonged disability. LCH may affect only one organ, with uni- or multifocal involvement or be multisystem disease involving multiple organs. The organs most frequently involved are bones, lung, skin and the endocrinal system. Pulmonary LCH is strongly related to smoking. Some patients have mixed histocytosis combining LCH and other histiocytic disorders. The diagnosis relies on the histological study of tissues samples, and shows tissue infiltration with large cell with pale cytoplasm and reniform nucleus, staining for CD1a and Langerin (CD207) on immunohistochemistry. The BRAFV600Emutation is observed in tissue samples in approximately half of patients and the activation of the RAS-RAF-MEK-ERK pathway has been shown to be constantly activated in LCH lesions, regardless the BRAF status. These findings represent an important forward step in the understanding of the physiopathology of the disease. Treatment must be adapted to the severity of the disease and goes from conservative observation to systemic chemotherapy. Therapies targeting the RAS-RAF-MEK-ERK pathway are promising treatments for progressive disease.
Assistance publique-Hôpitaux de Paris, hôpital Saint-Louis, département de médecine interne, 75010 Paris, France. Electronic address: mathilde.de-menthon@aphp.fr.
Mathilde
M
de Menthon
Assistance publique-Hôpitaux de Paris, hôpital Saint-Louis, Inserm UMR_S1165, service de pathologie, 75010 Paris, France.
Véronique
V
Meignin
Assistance publique-Hôpitaux de Paris, hôpital Saint-Louis, département de médecine interne, 75010 Paris, France; Université Paris-Diderot, Sorbonne Paris Cité, Inserm UMR 1153 CRESS, équipe de recherche en biostatistiques et épidémiologie clinique, 75010 Paris, France.
Alfred
A
Mahr
Université Paris-Diderot, Sorbonne Paris Cité, Inserm UMR 1153 CRESS, équipe de recherche en biostatistiques et épidémiologie clinique, 75010 Paris, France; Assistance publique-Hôpitaux de Paris, hôpital Saint-Louis, centre national de référence de l'histiocytose langerhansienne, service de pneumologie, 75010 Paris, France.
Abdellatif
A
Tazi
D000328:Adult; D017668:Age of Onset; D018450:Disease Progression; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology / Q000628:therapy; D006801:Humans; D008297:Male