Fig. 13. Histiocytosis of the chiasm and hypothalamus presenting as polydipsia, polyuria, hypersomnolence, and visual loss. Laboratory data were consistent with panhypopituitarism. Biopsy of the left frontal mass showed Langerhan-type histiocytosis. Contrast-enhanced magnetic resonance imaging shows a massively enlarged chiasm. (Job OM, Sehatz NJ, Glaser JS: Visual loss with Langerhans cell histiocytosis: multifocal central nervous system involvement. J Neuroophthalmol 19:49, 1999)