Epidemiology Unit, German Rheumatism Research Centre Berlin, Chariteplatz 1, 10117, Berlin, Germany. florian.milatz@drfz.de. Epidemiology Unit, German Rheumatism Research Centre Berlin, Chariteplatz 1, 10117, Berlin, Germany. Department of Paediatric Rheumatology, Helios Klinikum Berlin-Buch, Schwanebecker Chaussee 50, 13125, Berlin, Germany. Paediatric Rheumatology Clinics, University Hospital Eppendorf, Martinistraße 52, 20251, Hamburg, Germany. Department of Pediatrics, Division of Pneumonology and Immunology with intensive Medicine, Charité University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany. Paediatric Rheumatology Centre, Asklepios Clinic, Sankt Augustin, Arnold-Janssen-Straße 29, 53757, Sankt Augustin, Germany. German Centre for Paediatric and Adolescent Rheumatology, Gehfeldstraße 24, 82467, Garmisch-Partenkirchen, Germany. Epidemiology Unit, German Rheumatism Research Centre Berlin and Department of Rheumatology and Clinical Immunology, Charité University Medicine Berlin, Chariteplatz 1, 10117, Berlin, Germany.