[The apolipoprotein E genotype and Down's syndrome]

Some individuals with Down syndrome develop an Alzheimer-type dementia in the third and fourth decades of life. Dementia in Alzheimer disease has been associated with the presence of genotype epsilon 4/epsilon 4 in apolipoprotein E (apo E). By means of molecular analysis techniques genotypes in lipoprotein apo E were identified in 21 patients with Down syndrome. The results obtained showed that 76% of the studied population had the genotype epsilon 3/epsilon 3 and 9% genotypes epsilon 3/epsilon 4 and epsilon 2/epsilon 3. None of the cases was homozygous for the allele epsilon 4. The analysis of our data shows the absence of differences between the distribution of genotype apo E among the Down population studied and among general population. We therefore consider that the presence of the allele epsilon 4 has no influence on the manifestation of Alzheimer disease in patients with Down syndrome.