The consequences of disrupted PPi homeostasis are shown in the monogenetic disorders generalized arterial calcification of infancy (GACI, OMIM #208000), arterial calcification due to a deficiency in CD73 (ACDC, OMIM #211800) and pseudoxanthoma elasticum (PXE, OMIM #264800) [1]. This evidence concerns the gene NT5E and Pseudoxanthoma elasticum.