Competing interests: B Verstockt received lecture fees from Ferring and Takeda Pharmaceuticals. G Van Assche received financial support for research from Abbott and Ferring Pharmaceuticals; lecture fees from Janssen, MSD and Abbott; consultancy fees from PDL BioPharma, UCB Pharma, Sanofi-Aventis, Abbott, Abbvie, Ferring, Novartis, Biogen Idec, Janssen Biologics, NovoNordisk, Zealand Pharma A/S, Millenium/Takeda, Shire, Novartis and Bristol Mayer Squibb. S Vermeire received financial support for research from MSD, Abbvie, Janssen and UCB Pharma; lecture fees from Abbott,Abbvie, Merck Sharpe & Dohme, Ferring Pharmaceuticals and UCB Pharma; consultancy fees from Pfizer, Ferring Pharmaceuticals, Shire Pharmaceuticals Group, Merck Sharpe & Dohme, and AstraZeneca Pharmaceuticals. M Ferrante received financial support for research from Takeda and Janssen; lecture fees from Ferring, Boehringer- Ingelheim,Chiesi, Merck Sharpe & Dohme, Tillotts, Janssen Biologics, AbbvieTakeda, Mitsubishi Tanabe, Zeria; consultancy fees from Abbvie, Boehringer-Ingelheim, Ferring, Merck Sharpe & Dohme, and Janssen Biologics. SaV, HB, IC and MdB declare no conflicts of interest.