Some of the possible modifier alleles in the BBS-causing genes found in our cohort could be good candidates for functional studies to analyse a possible modifying effect on the BBS phenotype, e.g., IFT172, TRIM32, or WDPCP. Furthermore, we identified third alleles in other genes previously reported as possible candidates or modifiers of BBS, e.g., ALMS1, CORO2B, NPHP4, or PDE6B36,45–47. This evidence concerns the gene IFT172 and Bardet-Biedl syndrome.