Loss-of-function mutations in the catenin beta 1 (CTNNB1) gene lead to β-catenin deficiency, which is strongly associated with the CTNNB1 syndrome, a rare, monogenic, neurodevelopmental disorder marked by an array of motor and cognitive impairments with an estimated prevalence of around 2.6–3.2 in 100,000 live births.1 Here, CTNNB1 is linked to Cognitive impairment.