CTNNB1 and severe intellectual disability-progressive spastic diplegia syndrome: CTNNB1 syndrome, a rare autosomal dominant neurodevelopmental disorder, is caused by pathogenic loss-of-function (LoF) variants in the Ctnnb1 gene, which encodes the β-catenin protein, a critical regulator of the Wnt/β-catenin signaling pathway (Liu et al. 2022; Zhuang et al. 2023).