Footnotes

• Collaborators The following collaborators are members of the German IBD Study Group. They provided and cared for five or more study patients:

• Lars Helmstädter, Ingolf Schiefke, Tobias Klugmann, Oliver Bachmann, Manfred von der Ohe, Gisela Felten, Burkhard Bündgens, Thomas Klag, Dominik Bettenworth, Donata Lissner, Renate Schmelz, Jürgen Büning, Britta Siegmund, Christian Maaser and Martin Schmidt-Lauber.

• Contributors Conception or design of the work: NT and AS. Acquisition of data: NT, BB, WM, JW, CS and AS. Analysis of data: NT, TB, CS, and AS. Interpretation of data, drafting the work or revising it critically for important intellectual content and final approval of the version published: all authors. Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

• Competing interests None.

• Ethics approval The protocol has been approved by the Institutional Review Board at Jena University, Germany.

• Provenance and peer review Not commissioned; internally peer reviewed.