We examined 3 pairs of siblings with Bardet-Biedl syndrome in whom 3 different mutations in the BBS4 gene were detected, 2 of which were homozygous for the mutation.
A comparative study of the three Arab-Bedouin kindreds used to map the BBS2, BBS3, and BBS4 loci suggests that the variability in the number and severity of clinical manifestations, particularly the pattern of polydactyly, reflects chromosome-specific subtypes of BBS [Carmi et al., 1995a; Am J Med Genet 59:199-203].
The disorder showed statistically significant genetic linkage to the BBS4 locus on chromosome 15 in the affected siblings in two of the families, but the clinical features in these patients did not differ from the other cases of Bardet-Biedl syndrome.