ALZHEIMERS-DISEASE WITH AND WITHOUT COEXISTING PARKINSONS-DISEASE CHANGES - APOLIPOPROTEIN-E GENOTYPE AND NEUROPATHOLOGIC CORRELATES

The frequency of the apolipoprotein E (ApoE) epsilon 4 allele and its relationship with coexistent Parkinson's disease (PD) neuropathology i n Alzheimer's disease (AD) have not been extensively explored. We dete rmined ApoE genotype in 100 dementia patients with neuropathologically confirmed AD with and without concomitant Parkinson's disease (PD) ch anges (nigral degeneration and Lewy bodies at various sites). Fifty '' AD+PD'' patients were matched closely with 50 ''pure AD'' patients for age, sex, and duration of dementia. We found identical overrepresenta tion of the epsilon 4 allele in the two groups: 72% of the patients in each group had at least one ApoE epsilon 4 allele, compared with appr oximately 25% in the general population (p < 0.005) and in our institu tional autopsy population (p < 0.001). Age at onset varied inversely w ith epsilon 4 allele dosage in men but not in women in both the AD and the AD+PD groups. As with amyloid deposition and plaque frequency in AD, we observed an association between epsilon 4 dosage and PD-related changes. Specifically, the severity of ubiquitin-positive neuritic ch ange in CA2/3 of the hippocampus, but not the frequency of cortical Le wy bodies, varied significantly with epsilon 4 dosage in the AD+PD cas es.