ABCC6 and pseudoxanthoma elasticum (inherited or acquired): Furthermore, non-pathogenic polymorphisms have also been identified; for instance, an individual homozygous for the ABCC6 p.Arg1268Gln polymorphism did not show any PXE symptoms, and the Gln1268 (Q1268) allele was present at a frequency of 0.19 among healthy controls [31].