Prion infections in Creutzfeldt-Jakob disease and its variants.

Prions (PrP(Sc)) are proteinaceous infectious particles that occur as sporadic (85 percent), infectious (iatrogenic) (5 percent) or hereditary (10 percent) diseases in humans and animals. These unique infectious agents produce a spongiform change in the central nervous system without any inflammation, inclusion bodies or apparent antibody response. A helper (X) protein and genetic predisposition appear to be required to establish the infection, which seems associated with a post-translational change of a normal protein (PrP(C)) encoded by a gene on human chromosome 20. Sporadic human prion disease (Creutzfeldt-Jakob disease) is the most common form of human transmissible spongiform encephalopathy. Nevertheless, it is undoubtedly under-recognized as a result of both low autopsy rates and confusion with other dementing diseases like Alzheimer's disease. Although no therapy is currently available for this infectious dementia, which has a prolonged incubation period, these unfortunate victims should be offered supportive care and postmortem examinations. Universal precautions will protect laboratorians from this infectious, but not contagious, disease.