Polymorphism in AACT gene may lower age of onset of Alzheimer's disease.

The ApoE-epsilon 4 allele is a predisposing factor for late onset Alzheimer's disease (AD), however it is neither necessary nor sufficient to cause the disease. A candidate for explaining part of the remaining genetic component is alpha 1-antichymotrypsin (AACT). In a case-control study we genotyped a polymorphism within the AACT gene to test for association with the disease. No allele of this gene showed an increased incidence among the population with AD compared with controls, even when taking ApoE genotype into account. This contrasts with the results of a recently published report. The mean age of onset was apparently lowered by the presence of the AACT AA genotype among ApoE-epsilon 4 bearers. If AACT genotype has an effect on risk for AD it may be predominantly amongst individuals with early onset AD.