Familial Crohn's disease in Belgium: pedigrees, temporal relationships among cases, and family histories.

BACKGROUND

Recently we published an analysis of environmental factors in familial Crohn's disease (CD) in Belgium. The aim of the current study was to assess pedigrees and sibships, temporal relationships among cases, and family circumstances relevant to the frequency or onset of CD.

STUDY

Twenty-one families with 3 or more affected first-degree relatives were studied. Seventy-four patients with CD and 84 unaffected family members were interviewed together at the parental home, with the aid of a 176 item questionnaire. Pedigrees were constructed establishing which family members had the disease and their relationships within sibships. Dates of onset of disease, validation of first symptoms and circumstances potentially relevant to the onset and distribution of disease within families were among the data documented during the interviews. Sequence of disease within families, consecutive versus nonconsecutive sequence of disease within sibships, and temporal relationships among cases were tabulated.

RESULTS

In 12 of the 21 families CD occurred in a parent before CD in any children. Five affected fathers preceded 9 affected children; 7 affected mothers preceded 10 affected children. First borns were affected more frequently. Within sibships there were 21 instances (36%) when an affected sibling was consecutive in birth order with an affected sibling. When a parent had CD before the birth of the first child the "exposure interval" to CD in the children was longer (mean 22.4 y) than when the parent developed CD after the child was born (mean 11.8 y).

CONCLUSIONS

The clusterings of CD within sibships and in time suggest that there is a contagious element in the etiology of CD.