Whole-exome sequencing identified compound heterozygous variants in MMKS in a Chinese pedigree with Bardet-Biedl syndrome

Bardet-Biedl syndrome (BBS) is a genetically heterogeneous disorder characterized by retinal dystrophy, polydactyly, obesity, developmental delay, and renal defects. At least 21 candidate BBS-associated genes (BBS1-19, NPHP1, and IFT172) have previously been identified, and all of them play important roles in ciliary function. Here, we collected a BBS pedigree with four members and performed whole-exome sequencing on the proband. The variants were analyzed and evaluated to confirm their pathogenicity. We found compound heterozygous variants (c.1192C > T, p.Q398* and c.1175C > T, p.T392M) in MKKS in both the siblings, and these were likely to be pathogenic variants. We also found a missense variant (c.2029G > C, p.E677Q) in NPHP1 and a missense variant (c.2470C > T, p.R824C) in BBS9 in the proband only, which are variants of uncertain significance. The compound heterozygous variants were probably responsible for the BBS phenotype in this Chinese pedigree and the missense mutations in NPHP1 and BBS9 might contribute to the mutation load.