A population-based study of familial clustering of inflammatory bowel disease in Florence

In the frame of a population-based epidemiological study inthe metropolitan area of Florence in a 15 year period (1978–1992)all prevalent patients affected with ulcerative colitis (UC)or Crohn's disease (CD) (alive and resident in the area at theend of the study) were investigated in order to identify familialclustering. Only 45 patients (5.2%) reported at least 1 relativewith a diagnosis of inflammatory bowel disease (IBD). Amongthese, 25 patients reported a first-degree relative affectedwith IBD (2.9%). All the 28 families were contacted and detailedpersonal interviews were carried out in order to collect familytrees. The affected relatives living outside the study areawere also identified and their IBD diagnoses were verified.Fifteen families included only affected members with a diagnosisof UC; 5 had only CD, while 8 families had members affectedwith both forms. Two large families had 4 affected members and2 other families had 3. Overall 9 parent-child affected pairswere identified (1 out of every 3 families). The high concordancewithin families for the type of disease (p=0.015) suggests thatthe disease susceptibility is specific. The authors discussthese findings and a possible interpretation of the low proportionof familial cases in this area.