ABCC6 and Pseudoxanthoma elasticum: Although a number of genes may be involved (Li Q. et al., 2009; Omarjee et al., 2019; Boraldi et al., 2020a), PXE is mostly associated with ATP-binding cassette sub-family C member 6 (ABCC6) mutations (Le Saux et al., 2000), even though ABCC6 is not expressed at the protein level in cells of tissues undergoing calcification (Matsuzaki et al., 2005).