ABCC6 and Pseudoxanthoma elasticum: Furthermore, in contrast to the study published by Jansen et al.[20] where increased nucleotide/nucleoside concentrations in ABCC6-conditioned media and low inorganic pyrophosphate plasma concentrations in Abcc6 −/− mice were found, no significant differences were found in nucleoside triphosphate, nor in pyrophosphate (PPi) levels between PXE and control groups in this study.