aDepartment of Paediatric Rheumatology, Bristol Royal Hospital for Children, Bristol

bDepartment of Paediatrics, Royal United Hospital Bath, Bath

cMRC Integrative Epidemiology Unit and School of Population Health Sciences

dSchool of Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK

Correspondence to Prof. Athimalaipet V. Ramanan, FMedSci, Bristol Royal Hospital for Children, Upper Maudlin Street, Bristol BS2 8BJ, UK. E-mail: [email protected]