[Eosinophilic granuloma of bones in children].

Eosinophilic granuloma of bone or Langerhans cell histiocytosis is mostly unifocal. It appears on plain X Ray as a solitary destructive lesion of long bones or flat bones. CT is useful to define the extension to the cortical bone and also to precisely localize the lesion when the anatomy is complex (hip, spine, base of the skull). MR is very useful in case of more aggressive lesions when there is extension to soft tissues. Differential diagnosis includes circumscribed osteitis and tumors in the case of extensive destruction. The natural course of solitary lesions is favorable, spontaneously or with therapy. The prognosis is more serious in the case of multiple lesions.