title: Monozygotic twins with Crohn's disease and ulcerative colitis: a unique case report.
abstract: BACKGROUND
  A large number of monozygotic and dizygotic twin pairs with inflammatory bowel disease have been reported. To date no twin pair has developed phenotypically discordant inflammatory bowel disease. This case report is the first documented occurrence of discordant inflammatory bowel disease occurring in monozygotic twins.
  
  
  METHODS
  Twenty two year old identical male twins presented within three months of each other with inflammatory bowel disease that proved to be discordant in overall disease type, disease distribution, clinical course, and histopathological findings. Twin 1 developed a severe pancolitis necessitating total colectomy while twin 2 developed a predominantly distal patchy colitis with frequent granulomas, controlled by aminosalicylates. Twin 1 was antineutrophil cytoplasmic antibody (ANCA) negative at the time of testing while twin 2 (Crohn's disease) was ANCA positive. Significantly, the twins possessed the HLA type DR3-DR52-DQ2 previously associated with extensive colitis.
  
  
  CONCLUSIONS
  This case report confirms the important role played by genetic factors in the development of inflammatory bowel disease. It also highlights the crucial role of undetermined environmental agents in dictating disease expression and phenotype.
authors.affiliation: Department of Gastroenterology, Meath/Adelaide Hospitals, Dublin, Ireland.
authors.forename: N P
authors.initials: NP
authors.lastname: Breslin
authors.forename: A
authors.initials: A
authors.lastname: Todd
authors.forename: C
authors.initials: C
authors.lastname: Kilgallen
authors.forename: C
authors.initials: C
authors.lastname: O'Morain
mesh_terms: D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood; D003093:Colitis, Ulcerative / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D003106:Colon / Q000473:pathology; D003424:Crohn Disease / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D004200:Diseases in Twins; D006801:Humans; D007413:Intestinal Mucosa / Q000473:pathology; D008297:Male; D014430:Twins, Monozygotic
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic