title: Inflammatory bowel disease in a Swedish twin cohort: a long-term follow-up of concordance and clinical characteristics.
abstract: OBJECTIVE
  In 1988, we reported the first twin study in inflammatory bowel disease. The aim of the current study was to follow up these twins regarding new cases of inflammatory bowel disease and Crohn's disease characteristics using the Vienna classification.
  
  
  METHODS
  The official Swedish population register and the cause of death register were used to search for the twins. All living patients were interviewed.
  
  
  RESULTS
  Three monozygotic twins earlier classified as healthy had been diagnosed with inflammatory bowel disease (ulcerative colitis, n = 2; Crohn's disease, n = 1). Retrospectively, all 3 were symptomatic at the original survey. This changed the pair concordance in monozygotic twins from 6.3% to 18.8% in ulcerative colitis and from 44.4% to 50.0% in Crohn's disease. A high degree of concordance regarding age at diagnosis, disease location at diagnosis and during the course, and disease behavior was found in concordant monozygotic twin pairs with Crohn's disease. Seven of 9 pairs were identical in 3 or more of these disease characteristics compared with an expected number of 1.5 (P = 0.000076).
  
  
  CONCLUSIONS
  This study confirms that the genetic influence is stronger in Crohn's disease than in ulcerative colitis. A remarkable phenotype similarity within concordant pairs with Crohn's disease was found using the Vienna classification.
authors.affiliation: Division of Gastroenterology, Department of Medicine, Orebro University Hospital, S-701 85 Orebro, Sweden. jonas.halfvarson@orebroll.se
authors.forename: Jonas
authors.initials: J
authors.lastname: Halfvarson
authors.forename: Lennart
authors.initials: L
authors.lastname: Bodin
authors.forename: Curt
authors.initials: C
authors.lastname: Tysk
authors.forename: Eva
authors.initials: E
authors.lastname: Lindberg
authors.forename: Gunnar
authors.initials: G
authors.lastname: Järnerot
mesh_terms: D000328:Adult; D000368:Aged; D003093:Colitis, Ulcerative / Q000235:genetics; D003424:Crohn Disease / Q000235:genetics; D004200:Diseases in Twins; D005500:Follow-Up Studies; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000235:genetics*; D008875:Middle Aged; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic