ABCC6 and pseudoxanthoma elasticum (inherited or acquired): ABCC6 is a transmembrane protein primarily expressed in the liver and kidney, where through an unknown mechanism it exports ATP, among other substrates, into the circulation.(8) Membrane‐bound ENPP1 catalyzes the hydrolysis of ATP to AMP, generating PPi, which in turn inhibits mineralization.(12, 31) The functional loss of ABCC6 or ENPP1 thereby results in reduced serum PPi and AMP levels, leading to systemic ectopic calcification as seen in mouse models and patients with PXE and/or GACI.(7, 11, 32)