The observation of low levels of carboxylated anticalcifying factors in the blood of PXE and the report of PXE phenocopy due to a defect in vitamin K dependent γ-glutamyl carboxylase (GGCX) in humans [63], suggested a possible role for vitamin K in PXE. The gene discussed is GGCX; the disease is autosomal recessive inherited pseudoxanthoma elasticum.