Table 1

Family cohort used in the study: affected sibling pairs are ordered according to the size of the sibship and disease type (mixed refers to sibships with both ulcerative colitis (UC) and Crohn's disease (CD)). The number of families and affected sib pairs (in parentheses) are given in each category. In 55% of the 268 families, both parents were available for analysis.

Sibship sizeCDUCMixed (CD/UC)Total
2114 (114)78 (78)38 (38)230 (230)
3 14 (42)12 (36) 9 (27) 35 (105)
4  1 (6) 2 (12)  3 (18)
All129 (162)90 (114)49 (77)268 (353)