NT5E and pseudoxanthoma elasticum (inherited or acquired): 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].