Prion diseases, ortransmissible spongiform encephalopathies (TSEs),are a class of rare and fatal infectious neurodegenerative disorderscharacterized by brain vacuolation, neuronal loss, and cognitive andmotor impairments.1 Etiological agentsresponsible for TSEs are prions, novel infectious agents derived fromthe physiological membrane-bound cellular prion protein (PrPC).2,3 When PrPC acquires its misshapen state(referred to as PrPSc), it tends to form aggregates, imposingits anomalous structure on the benign PrPC molecules. The gene discussed is PRNP; the disease is prion disease.