prion disease, any of a group of fatal degenerative diseases of the nervous system caused by abnormalities in the metabolism of prion protein. These diseases are unique in that they may be transmitted genetically as an autosomal-dominant trait or by infection with abnormal forms of the protein (prions). Inherited forms result from mutations in the gene that codes for prion protein; such mutations may occur sporadically. Hereditary forms include some forms of Creutzfeldt-Jakob disease, Gerstmann-Sträussler syndrome, and fatal familial insomnia. Infectious forms of the disease result from ingestion of infected tissue or the introduction of infected tissue into the body (kuru and some forms of Creutzfeldt-Jakob disease). The latter has occasionally occurred during surgical procedures. It has also occurred as the result of injection of human growth hormone prepared from infected pituitary glands. Prion diseases also occur in animals. Also called subacute spongiform encephalopathy, transmissible neurodegenerative disease, transmissible spongiform encephalopathy.
