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Increased incidence of sporadic Creutzfeldt-Jakob disease on the island of Crete associated with a high rate of PRNP 129-methionine homozygosity in the local population



Since the spring of 1997, when the Neurology Department of the University Hospital of Crete admitted its first patient, 9 cases (8 neuropathologically confirmed and 1 probable) of sporadic Creutzfeldt-Jakob disease (sCJD) have been recorded. This represents an annual incidence five-fold higher than expected based on the island's population (0.54 million). Molecular analysis of the prion-protein gene (PRNP) showed no mutations in any of the seven CJD cases studied. Five patients (ages 64–88 years) were homozygous for methionine-129 of PRNP and showed the classic sCJD triad (subacute dementia, myoclonus, periodic electroencephalogram). Brains contained Type 1 (unglycosylated 21.5 kDa band) protease-resistant prion protein (PrPres). Two patients (ages 56 and 57 years), both homozygous for valine-129, showed cerebellar ataxia and later dementia not associated with periodic electroencephalogram; brain PrPres was Type 2. Genotyping of 205 Cretan controls showed that methionine-129 homozygosity, a susceptibility factor for sCJD, was significantly higher in this population than in other Caucasian populations (57.0%, n = 205 versus 41.5%, n = 859. These data are the first to relate a high regional incidence rate for sCJD to the distribution of PRNP 129 genotypes in the local population; however, additional factors may be operational.

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