It could very well be that the effects of the different SNPs in ABCB1 that we have found in AD patients are physiologically effectuated through the linkage disequilibrium via the G2677T SNP, which is a non-synonymous variant, thus changing amino acid sequence, while the mutations in C1236T and C3435T are synonymous [5,6]. This evidence concerns the gene ABCB1 and Alzheimer disease.