INFLAMMATORY BOWEL-DISEASE IN 67 FAMILIES EACH WITH 3 OR MORE AFFECTED FIRST-DEGREE RELATIVES

Background & Aims: Some families have multiple members with inflammato ry bowel disease (IBD). Do clinical features of familiar differ from s poradic cases? Is there concordance between affected family members? D o environmental factors affect familial clustering? Methods: In 67 fam ilies, each with three or more first-degree relatives with IBD, the 21 3 affected family members were interviewed, and their case records wer e reviewed, Results: The clinical manifestations of familial cases did not differ from IBD reported ire a large series, There was concordanc e for type of disease (P < 0.001) but not greater than expected concor dance for age at diagnosis, site and extent of disease, or transmural aggressiveness of Crohn's disease, A significant association between s moking with Crohn's disease and nonsmoking with ulcerative colitis was found (P < 0.001), even in families with both disorders. The interval s between diagnosis of successive family cases varied so greatly that a single etiologic factor with a constant latent period seems to be un likely, When IHD affected successive generations, parents were diagnos ed at a later age than the children (P < 0.001) and after the child in 12 of 49 cases, Conclusions: Analysis has not identified any clinical ly significant differences between familiar and sporadic cases of IBD, Tobacco smoking affects disease type in familial cases.