Diagnosis: This patient has a familial form of Creutzfeldt-Jakob disease (CJD) - a spongiform encephalopathy caused by protease-resistant proteins (PrPs - otherwise know as prions). The rapidly progressive dementia and myoclonus are the hallmarks of CJD, which mostly affects persons between the ages of 50 and 75 years, but patients as young as 16 and as old as 80 have been reported. The disease is usually fatal within 6 months of onset. About fifteen percent of CJD patients have a family history of the disease consistent with an autosomal dominant mode of transmission. In addition to the brain, PrPcjd has been found in the CSF, lymph nodes, liver, kidney, spleen, and lung of patients with CJD. Human-to-human transmission has occurred via corneal transplants, implantation of EEG electrodes, by cadaveric dura matter grafting, and by the parenteral administration of growth hormone prepared from cadaveric human pituitary glands.There is no effective treatment.