Two-octapeptide repeat deletion of prion protein associated with rapidly progressive dementia.

Insertions of integral numbers of an octapeptide repeat in the prion protein gene are pathogenic mutations associated with inherited prion diseases. Conversely, deletions of a single octapeptide repeat are found as normal polymorphisms in many populations and do not predispose individuals to prion disease. The authors report a two-octapeptide repeat deletion in an elderly woman with a rapidly progressive dementia consistent with Creutzfeldt-Jakob disease. This mutation was absent from more than 3,000 individuals and may be causally related to prion disease and represent a novel disease mechanism.