Pseudoxanthoma Elasticum (PXE) Natural History Biomarkers in PXE Individuals and Their Biological Non-PXE Siblings

Inclusion Criteria: * Male or female participants aged 18 to 75 years * Participants (approximately 1 carrier and 1 normal to match proband) * Confirmed PXE participants: index PXE/proband with established PXE and ABCC6 mutations identified * PXE carrier participants: biological sibling of the PXE index case and confirmed as PXE carrier * Non-PXE normal participants: biological sibling of PXE index case and confirmed as non-PXE normal Exclusion Criteria: * Unconfirmed ABCC6 mutation status * Use of bisphosphonate in the preceding 12 months and during the study * Use of Vitamin B6 and/or Vitamin D supplement in the preceding 1 month and during the study (if the total Vitamin B6 supplementation is \>5 mg/day) * Recent initiation or dose change of Vitamin D and/or multivitamin supplement in the preceding 1 month and during the study * Bone fracture within 3 months prior to Screening or active bone disease (excluding osteopenia or osteoporosis) * History of hyperparathyroidism * History of moderate to severe renal impairment * History of hypophosphatasia * Known history of uncorrected abnormality in calcium (Ca), phosphate, alkaline phosphatase (ALP) or parathyroid hormone * Other significant condition (medical, psychiatric, social, or medication) that, in the judgment of the Investigator, would prevent full participation or would be inappropriate for the study