ENPP1 and calcification: The presence of cardiac hypertrophy in old Abcc6−/− mice [64] and the well-characterized dystrophic cardiac calcification in animal models [83,84,88] suggest that the PXE patients could well be susceptible to cardiopathy when comorbidities are present as changes to the cardiac purine metabolism via elements of the ABCC6 → ENPP1 → CD73 → Adenosine pathway could be responsible for the pathological cardiac manifestations reported in the many case reports involving PXE or GACI [225,226,227,228,229,230].