<unk>  is a very rare, invariably fatal degenerative neurological disorder of the brain. It is caused by the presence of a prion protein, an abnormal isoform of a cellular glycoprotein.<unk>  may be classified into either sporadic, familial and iatrogenic forms.  The sporadic form may be further categorized into either classic or variant<unk> . The majority of cases of<unk>  are thought to occur sporadically from prions by an unknown route of transmission. Reports on transmission by human growth hormone products, grafting, surgical electrode implantation, and consumption of infected products have been described. Once transmitted, the<unk>  prion promotes refolding of the native proteins into the<unk> d state. The number of misfolded protein molecules increases exponentially, and the process leads to a large quantity of insoluble prions in the affected cells, resulting in cell death. Risk factors for<unk>  include advanced age, positive family history, personal history of psychosis, history of surgical procedures, grafts or implants, and history of ingestion of human growth hormones or contaminated meat. Once symptoms develop,<unk>  is rapidly progressive and almost always fatal. Early symptoms are often non-specific. Patients' relatives usually report rapidly progressive dementia, personality changes,  uncontrolled sporadic laughter, and sleep disorders. The majority of patients (85% of patients) die within 1 year of symptom-onset. Common complications of<unk>  include overwhelming infections, congestive heart failure, or respiratory failure. The diagnosis of<unk>  depends on a combination of positive findings from physical examination and laboratory testing. Based on the findings, the diagnosis of<unk>  may be either probable or possible. There are no definitive criteria for the diagnosis of<unk> . Typical EEG findings in<unk>  include periodic biphasic or triphasic sharp wave complexes (PSWCs). Periodic synchronous discharges (PSDs) occur either before or in synchronicity with myoclonus. Biopsy of the brain tissue is the definitive diagnostic test for<unk> , but is not usually performed. Management of<unk>  is directed towards palliative care. There is no effective treatment or vaccine for<unk> .
Creutzfeldt-Jakob disease
Bickerstaff's encephalitis
Carnevale-Canun-Mendoza syndrome
Bovine spongiform encephalopathy
AIDS dementia complex
Pick's disease
Wernicke-Korsakoff syndrome
St. Louis encephalitis