The observations that: (i) MGP levels were decreased in the serum of PXE patients compared to non-carriers (15), (ii) the concentration of MGP in the serum of Abcc6−/− mice was similarly reduced when compared to wild-type animals and (iii) most of the MGP isolated from the liver of Abcc6−/− mice was largely under-carboxylated, thus exhibiting reduced or no activity (16), suggested a possible pathogenic role of vitamin K in PXE (17). This evidence concerns the gene MGP and Pseudoxanthoma elasticum.