Limb disorders

Gene: IFT57

Green List (high evidence)

Comment on list classification: There are 2 unrelated individuals reported in literature with bialellic IFT57 variants and polydactyly. Functional evidence from a knockout mouse model supports this gene-phenotype association. Hence, this gene should be promoted to Green on Limb disorders at the next update.

Created: 26 May 2026, 1:06 p.m. | Last Modified: 26 May 2026, 1:06 p.m.

Panel Version: 8.6

PMID: 27060890 Thevenon et al., 2016
3 sibs aged 17-25 years, from a consanguineous family, with oral-facial-digital syndrome with skeletal dysplasia, polydactyly, and brachymesophalangia. No visual complaints, retinopathy not excluded in the study. All homozygous for IFT57 p.Lys259Lys. It is rare in gnomAD v4., no homozygotes reported. Variant leads to exon skipping, decrease in mRNA stability. Both anterograde ciliary transport and sonic hedgehog signaling were significantly decreased in subjects’ fibroblasts compared to controls.

PMID:40273360 Nitoiu et al., 2025
Report of a 29-year-old male of Irish descent presenting with rod-cone degeneration leading to legal blindness, post-axial polydactyly, obesity, cognitive impairment, and fatty liver, features suggestive of a clinical diagnosis of Bardet-Biedl Syndrome. He was identified with biallelic variants in IFT57 gene (Val397Glu/Lys225Asnfs*17).

Patient-derived fibroblasts had fewer primary cilia, abnormal ciliary morphology and abnormal anterograde transport in the primary cilia. IFT57 knockout mouse models or RPE cell lines did not form primary cilia. Rescue of IFT57 knockout primary cilia with IFT57-WT restored cilia formation while IFT57-Val397Glu only partially rescued cilia formation in Ift57-KO-mouse cells.

PMID: 17027958 Houde et al., 2006
IFT57-/- knockout mouse (old gene name Hippi) only survived roughly until E9.5. One embryo survived until E13.5, and showed exencephaly, hypotelorism, and polydactyly on both fore and hind limbs.

Sources: Literature

Created: 7 May 2026, 1:28 p.m. | Last Modified: 26 May 2026, 1:05 p.m.

Panel Version: 8.6

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
?Orofaciodigital syndrome XVIII, OMIM:617927; ciliopathy, MONDO:0005308

Publications

• 17027958
• 27060890
• 40273360