Identification of a novel splice mutation in CTNNB1 gene in a Chinese family with both severe intellectual disability and serious visual defects, Abstract The CTNNB1 gene encode the β-catenin protein which is a core unit of the cadherin/catenin multiprotein complex. The loss-of-function mutation of the CTNNB1 gene recently has been confirmed as a cause of intellectual disability. Previous studies have found that patients with CTNNB1 gene mutation may have other clinical manifestation such as microcephaly, abnormal facial features, motor and language delays, and mild visual defects. Here, we reported a 27-year-old Chinese pregnant woman with a severe intellectual disability and serious visual defects who was detected with a novel splice mutation (c.734+1G>A) in CTNNB1 gene by whole-exome sequencing and confirmed by Sanger sequencing. Further investigation showed that the variant was inherited from her mother with similar phenotypes. This report not only helps to expand the mutant spectrum of the CTNNB1 gene but also prompts a new insight into genetic diagnosis in patients with both serious intellectual disability and visual defects.