1 Rheumatology and Bone Disease Unit (S.H.R.), Centre for Genomic and Experimental Medicine, Institute of Genetics and Molecular Medicine, University of Edinburgh,Western General Hospital, Edinburgh, United Kingdom; Hospital el Bierzo (L.C.-G.), Ponferrada, Spain; Department of Medicine (W.D.F.), University of E Anglia, Norwich, United Kingdom; Department of Internal Medicine (L.G.), Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy; Metabolic Bone Diseases Unit (N.G.), Service of Rheumatology, Hospital Clinic, University of Barcelona, Barcelona, Spain; Institute of Human Development (P.L.S.), Faculty of Medical and Human Sciences, University of Manchester; Manchester Royal Infirmary, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom.