NPHP4 and Bardet-Biedl syndrome: 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.