Third case of Bardet-Biedl syndrome caused by a biallelic variant predicted to affect splicing of IFT74

Clin Genet. 2021 Jul;100(1):93-99. doi: 10.1111/cge.13962. Epub 2021 Mar 27.


Bardet-Biedl syndrome (BBS) is a rare ciliopathy characterized by rod-cone dystrophy, postaxial polydactyly, truncal obesity and renal anomalies with autosomal recessive inheritance. We describe a 6-year-old male with early onset retinal dystrophy, postaxial polydactyly, truncal obesity and motor delays. Exome sequencing revealed a homozygous variant predicted to affect splicing of the IFT74 gene, c.1685-1G > T. This is the third patient with BBS due to variants predicting loss of function in IFT74. All three patients have had retinal dystrophy, polydactyly, obesity, developmental differences, and a notable lack of renal anomalies. We recommend that IFT74 is added to gene panels for the diagnosis of BBS.

Keywords: Bardet-Biedl syndrome; IFT74; ciliopathy; obesity; polydactyly; retinal dystrophy.

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Alleles
  • Bardet-Biedl Syndrome / genetics*
  • Child
  • Cytoskeletal Proteins / genetics*
  • Exome / genetics
  • Exome Sequencing / methods
  • Fingers / abnormalities
  • Genetic Variation / genetics*
  • Humans
  • Male
  • Phenotype
  • Polydactyly / genetics
  • RNA Splicing / genetics*
  • Retina / pathology
  • Retinal Dystrophies / genetics
  • Toes / abnormalities


  • Cytoskeletal Proteins
  • IFT74 protein, human

Supplementary concepts

  • Polydactyly, Postaxial