1 Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genoa, Genoa, Italy.
2 Department of Rheumatology, Ghent University Hospital, Ghent, Belgium.
3 Department of Internal Medicine, Ghent University, Ghent, Belgium.
4 Centre for Musculoskeletal Research, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK.
5 Hamburg Centre for Pediatric and Adolescent Rheumatology, Schön Klinik Hamburg Eilbek, Hamburg, Germany.
6 Biostatistics Unit, Department of Public Health, Ghent University, Ghent, Belgium.
7 Department of Rheumatology, University Hospital Zurich, Zurich, Switzerland.
8 Division of Rheumatology, Instituto Gaetano Pini, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
9 Department of Dermatology, Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium.
10 Department of Dermatology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
11 Department of Immunology and Allergology (CIA), Centre Hospitalier Universitaire (CHU) Brugmann, Université Libre de Bruxelles (ULB), Brussels, Belgium.
12 Department of Rheumatology and Clinical Immunology, Kerckhoff Clinic Bad Nauheim, Bad Nauheim, Germany.
13 Department of Internal Medicine and Rheumatology, Justus-Liebig University Giessen, Giessen, Germany.
14 Department of Internal Medicine and Medical Specialities, University Sapienza Rome, Rome, Italy.