PROS1 and chronic kidney disease: Patients with chronic kidney disease (CKD) have an extremely high risk of developingvascular disease,1 and vascular calcificationis an independent risk factor for cardiovascular mortality.2 Thus, vascular calcification is important for the prognosis of CKD.Clinically, vitamin D and K deficiencies are known to be risk factors for uremic vascularcalcification.3,4 Vitamin K comprises a group of fat-soluble vitamins that act as co-factors forγ-glutamylcarboxylase, which activates several vitamin K-dependent proteins.