Genetic association between susceptibility to Parkinson's disease and α₁-antichymotrypsin polymorphism

The apolipoprotein E (ApoE) gene is a major risk factor of developing Alzheimer's disease (AD) and the α₁-antichymotrypsin (ACT) polymorphism is likely to modify susceptibility of the ApoE gene for AD. Because pathogenesis of AD is partly similar to that in idiopathic Parkinson's disease (PD), we investigated the distribution of genotypes of the ApoE and the ACT in patients with PD. The number of individuals with two copies of the ACT-A allele (ACT-AA genotype) in patients with PD increased significantly compared to that in healthy controls (19.9% versus 8.3%, P < 0.02), and the ACT-A allele frequency in patients with PD was significantly higher than that in healthy controls (X² = 5.96, df = 1, P < 0.015). The odds ratio for developing PD in individuals with the ACT-AA genotype was 3.36 compared to individuals with two copies of another allele, the ACT-T allele (ACT-TT genotype). There was no association between ApoE genotypes and susceptibility to PD. These data suggest that the etiological basis of PD might be partly similar to that of AD and the ACT gene might be one of the susceptibility factors for PD.