The causative mutations for BBS have been mapped to about 26 genes, however, mutations in BBS1 to BBS 18 in about 70–80% of cases worldwide, mutations in BBS1 and BBS 10 are detected in 21–30% of patients, a proportion that rises to 40–50% in Northern European patients. Here, BBS2 is linked to Bardet-Biedl syndrome.