title: Histiocytosis X.
abstract: Histiocytosis X is characterized by a proliferation of cytologically benign histiocytes and occurs in a severe form (type 1) with a short course and poor prognosis and a milder form (type 2) with a protracted course and favorable prognosis. Otolaryngologists will encounter the type 2 form of the disease and must include it in the differential diagnosis of osteolytic lesions of the skull.
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001847:Bone Diseases / Q000145:classification / Q000175:diagnosis* / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000145:classification / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D011379:Prognosis; D013701:Temporal Bone / Q000473:pathology*