Evidence of linkage in families of bipolar patients has so far been identified with genetic markers on chromosome X and 11. However, replications of these data have not consistently been reported in either case, which favours the hypothesis of genetic heterogeneity. Therefore, we have tried to outline a sampling strategy for linkage replication in affective disorders. We estimated the average number of nuclear families required to replicate X or 11 linkage as a function of the degree of heterogeneity as well as the number to prove heterogeneity given that linkage exists. The results are presented and discussed.

Coeliac disease (CD) is a malabsorptive disorder of the small intestine resulting from ingestion of gluten. The HLA risk factors involved in CD are well known but do not explain the whole genetic susceptibility. Several regions of potential linkage on chromosomes 3q, 5q, 10q, 11q, 15q and 19q have already been reported in the literature. These six regions were analyzed with the Maximum Lod Score method on a dense set of markers. A new sample of 89 Italian sibpairs was available for study. There was no evidence for linkage for any of the regions tested, except for chromosome 5q. For this region, our data, as well as a sample of 93 sibpairs from our first genome screen (Greco et al. 1998), are compatible with the presence of a risk factor for CD with a moderate effect.