PRNP Val129 homozygosity increases risk for early-onset Alzheimer's disease.

We analyzed the PRNP M129V polymorphism in a Dutch population-based early-onset Alzheimer's disease sample. We observed a significant association between early-onset Alzheimer's disease and homozygosity of M129V (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.1-3.3; p = 0.02) with the highest risk for V homozygotes (OR, 3.2; 95% CI, 1.4-7.1; p < 0.01). In patients with a positive family history, these risks increased to 2.6 (95% CI, 1.3-5.3; p < 0.01) and 3.5 (95% CI, 1.3-9.3; p = 0.01), respectively.