1. From the Center for Human Genetic Research and Neurology Department (K.S.), Massachusetts General Hospital and Harvard Medical School, Boston, Mass; Neurology Service (J.P.), Juan Fernandez Hospital, Quilmes, Buenos Aires, Argentina; Departments of Neurology and Pediatrics (M.B.), Columbia University College of Physicians and Surgeons, New York; Charles Dent Metabolic Unit (P.L.), National Hospital for Neurology & Neurosurgery, Queen Square, London UK.