Unifocal Langerhans' cell histiocytosis (eosinophilic granuloma) of the petrous apex.

Eosinophilic granuloma is a localized form of histiocytosis X, or Langerhans' cell histiocytosis, a benign lesion of proliferating Langerhans' cells. It is the least severe of the histiocytosis syndromes, and is characterized by lytic lesions of one or more bones. Temporal bone lesions usually occur in association with multifocal disease; however, isolated lesions may occur in either the mastoid bone alone, or in the entire temporal bone, without disease elsewhere in the body. We present the first case (to our knowledge) of eosinophilic granuloma, or unifocal Langerhans' cell histiocytosis, limited to the petrous apex. The patient, an 8-year-old girl, presented with facial nerve paralysis. Because of delay in definitive diagnosis, the disease extended beyond its original boundaries and resulted in complete destruction of the temporal bone. We will also review Langerhans' cell histiocytosis, with attention to its involvement of the temporal bone.