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Ice-nine and human prion disease.

More than 35 years ago, Kurt Vonnegut described an endgame weapon, “ice-nine,’’ in his novel Cat’s Cradle. Ice-nine was a super-crystal of water that caused any water with which it had contact to freeze at room temperature. Thus, a minute quantity of ice-nine could transform all the water on earth to its crystalline structure (i.e., ice), which would be incompatible with life. A group of previously obscure neurodegenerative diseases has recently been found to involve frightening transformative properties reminiscent of icenine. These disorders, characterized by progressive neurodegeneration, “spongiform” pathology in the cerebral cortex (which reflects the punctate deposition of protein aggregates in the brain parenchyma), and dementia, have attracted increasing attention with the occurrence of an epidemic of a new variant, bovine spongiform encephalopathy (BSE), in Great Britain. Of particular concern is the evidence that BSE has been transmitted to humans.2 Since the majority of humans with this disorder have initially been treated by psychiatrists for apathy, depression, and delusions, BSE and related spongiform encephalopathies have considerable relevance to psychiatry. This column reviews the recent advances in the neurobiology of BSE and related disorders. The spongiform encephalopathies, which were previously thought to be due to “slow viruses,” include CreutzfeldtJakob disease (CJD), kuru, and scrapie. CJD is a rare (one death per million per year in the United States), late-onset, hereditary dementia that can also be transmitted to other individuals by direct exposure to the tissue from an affected individual-pituitary extracts and corneas, for example. Kuru, a neurodegenerative disorder among the Fore people in Papua New Guinea, appears to have been perpetuated and transmitted because of the custom of the women and children to consume the brains of deceased relatives. Scrapie is a neurodegenerative disorder that affects sheep, resulting