A polymorphism in the presenilin 1 gene does not modify risk for Alzheimer's disease in a cohort with sporadic early onset.

Mutations in the presenilin 1 gene account for many cases of early onset familial Alzheimer's disease. Homozygosity for the 'T' allele of a polymorphism in the presenilin 1 gene has previously been reported to double the risk for Alzheimer's disease in a late onset Caucasian sample. Here we report that this polymorphism does not incur risk in a case control sample of early onset Alzheimer's disease, possibly suggesting a different disease etiology between the early and late onset forms.