ABCC6 and pseudoxanthoma elasticum (inherited or acquired): According to the mechanisms involved in pseudoxanthoma elasticum, due to mutations in ABCC6 accounting for low [PPi]pl (Le Saux et al., 2000) and vascular calcification (Leftheriotis et al., 2013), it could be that the production of PPi related to ABCC6 was decreased in our patients.