1. Department of Neurology, VU University Medical Centre, Amsterdam, The Netherlands.
2. Laboratory of Immunogenetics, VU University Medical Centre, Amsterdam, The Netherlands.
3. Aragonés Institute of Health Sciences and Department of Gastroenterology, Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain.
4. Department of Gastroenterology, VU University Medical Centre, Amsterdam, The Netherlands.
5. Department of Radiology, VU University Medical Centre, Amsterdam, The Netherlands.
6. Department of Epidemiology and Biostatistics, VU University Medical Centre, Amsterdam, The Netherlands.