Stuart H Ralston1, Georg Schett2. 1. Centre for Genomic and Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK. stuart.ralston@ed.ac.uk. 2. Department of Internal Medicine 3, Rheumatology and Immunology, Friedrich Alexander University Erlangen-Nuremberg and Universitatsklinikum Erlangen, Ulmenweg 18, 91054, Erlangen, Germany.