Unifocal Langerhans' cell histiocytosis in the clivus of a child with abducens palsy and diplopia.

Histiocytosis X, described by Lichtenstein in 1953, is an uncommon disorder that is characterized by an abnormal proliferation of Langerhans' cells. The Langerhans' cell normally occurs in the epidermis and T-cell-dependent areas of lymph nodes and functions as a macrophage. Histiocytosis X is predominantly a disease of childhood but can occasionally be seen in adults. Eosinophilic granuloma of the skull is the most common presentation of the disease, and the associated symptoms depend on the location of the lesion. It has been reported to occur in the temporal bone, including the petrous apex. We present the first reported case, to our knowledge, of eosinophilic granuloma, or unifocal Langerhans' cell histiocytosis, in the clivus of a child.