Identifiee il y a plus d'un siecle, l'histiocytose langerhansienne reste une affection enigmatique. Son large spectre clinique est caracteristique, des formes agressives du nourrisson se presentant comme une hemopathie au granulome eosinophile osseux solitaire. L'histiocytose langerhansienne est une proliferation clonale d'histiocytes proches des cellules presentatrices d'antigenes de la peau, les cellules de Langerhans. En depit d'une meconnaissance de la physiopathogenie, des progres therapeutiques ont ete realises grace a l'individualisation des facteurs de risque et une stratification des patients, aide a la strategie de traitement. Les formes localisees justifient habituellement d'une simple surveillance. Les formes multiviscerales, objet d'une recherche clinique et biologique intense, ont un pronostic tres reserve et beneficient actuellement d'essais randomises de l'Histiocyte Society.
Although Langerhans cell histiocytosis (LCH) was described a century ago, its cause and pathogenesis are still unknown. A wide spectrum of disease and variable clinical behavior are characteristic. The clinical varieties of this enigmatic disease range from a lethal leukemia-like disorder that primarily affects infants to a curable solitary lytic lesion of bone. LCH is a clonal proliferative disorder of histiocytes that resembles in morphology and phenotype the dendritic antigen-presenting Langerhans' cells of the skin and other organs. Despite gaps in understanding, significant improvements in the therapies for this disease have been made. Careful risk stratification is critical for the appropriate administration of therapy. Patients with good prognostic factors may need only observation as their disease spontaneously regresses, or minimal intervention. The active search for more effective treatments for patients with poor prognostic features is a major future challenge for the Histiocyte Society.