HLA-A2 as a possible marker for early-onset Alzheimer disease in men.

We performed HLA typing on 36 patients with clinically diagnosed Alzheimer disease and 25 controls. Antigen A2 was present in all ten men (100%) with early-onset (less than 60 years) dementia, a frequency significantly higher than the 30% frequency found in the cognitively intact men of a comparable age (p = 0.009, corrected). This increased A2 frequency was also significantly greater than the frequencies for all other patient subgroups, including late-onset men (40%, p = 0.008), early-onset women (44%, p = 0.004), and late-onset women (42%, p = 0.028). Our findings, if repeated in future studies with larger samples, suggest that HLA-A2 positive men may comprise a subgroup with increased susceptibility to early-onset disease.