The first such study was published in 2009, initially with 1896 cases and 1939 controls and a replication phase with 2457 cases and 2654 controls, and showed an association between a locus on 9q34 and PCa marked by the SNP rs505922 (OR 1.20), mapped on the first intron of the ABO blood group gene, which shed light on the genetic epidemiology of PCa [64]. The gene discussed is ABO; the disease is posterior cortical atrophy.