Langerhans cell histiocytosis of the perianal region.

Examination of the archived charts confirmed this. Indeed, 11 years prior to this incident he had attended a neurosurgical unit with a two-year history ofproptosis affecting the right eye. Routine neurological examination was normal except that his right eye was displaced downwards and forwards. A CT scan showed destruction of the bone in the right anterior frontal region with a soft tissue mass extending into the anterior cranial fossa, in keeping with an extra-dural mass. A right frontal craniotomy had been performed and the lesion was removed in a piecemeal fashion. It was felt at the time of the procedure that not all the lesion had been excised; however, the bony defect was repaired with titanium gauze. Two months later he underwent a course of chemotherapy, consisting of prednisolone, vincristine followed by mercaptopurine. One year later he developed diabetes insipidus. However a repeat CT scan had shown no pituitary involvement. He responded well to nasal desmopressin. A repeat CT scan six months later showed no evidence of further disease and he subsequently underwent a titanium cranioplasty to cover the bony defect. He was kept under review with no evidence of recurrence and a MRI four years later showed no evidence ofrecurrence of disease.