Inclusion Criteria:  Individuals eligible to participate must meet all of the following inclusion criteria:  Must provide written or electronic consent (if able) and/or the consent of the legally authorized representative/caregiver and assent for subjects <18 years of age after the nature of the study has been explained and prior to any research-related procedures, following the policies of the clinical site Clinical diagnosis of ENPP1 Deficiency or the early-onset form of ABCC6 Deficiency (GACI 2) based on clinical, radiological, or biochemical evidence and confirmed by prior or concurrent genetic testing. The early-onset form of ABCC6 Deficiency is defined as diagnosis of GACI 2 before 5 years of age for subjects of any age at enrollment. Male or female, birth through adulthood In the opinion of the Investigator, must be willing and able to complete all aspects of the study Agree to provide access to relevant medical records.  Exclusion Criteria:  Individuals who meet the following exclusion criterion will not be eligible to participate:  In the opinion of the Investigator and/or Sponsor, presence of any clinically significant disease (outside of those considered associated with the diagnosis of ENPP1 Deficiency or the early-onset form of ABCC6 Deficiency [GACI 2]) that precludes study participation or may confound interpretation of study results, such as an unrelated bone, mineral, or muscle disease or genetic connective tissue disease Receiving any investigational new drug or device or plans to do so before completion of participation in the study. Participation in an interventional trial of an approved drug or device being used in an investigational manner is allowed, depending on review and approval of the Sponsor