The CTNNB1 syndrome (MIM # 615075) is a neurodevelopmental disorder with variable expressivity, caused by variants in the CTNNB1 gene, located on chromosome 3.

Main clinical features
It is characterized by a variable degree of cognitive impairment, microcephaly, truncal hypotonia, peripheral spasticity, visual defects and dysmorphic features.

According to the Deciphering Developmental Disorders Study, CTNNB1 ranked amongst the ten commonest genes with de novo variants in individuals with developmental delay. The prevalence cannot be ascertained with precision yet but is estimated to be 2.6-3.2 per 100,000 births.

The disorder is inherited in an autosomal dominant manner. The majority of variants occur de novo but can also be inherited from an affected parent.