The present paper provides a comprehensive and up-to-date review of published cases of CTNNB1 Syndrome, an analysis of the prevalence of the most common symptoms, and a classification of CTNNB1-associated mutations according to the severity of their respective phenotypes (Table 5, Table 6 and Table S1, Supplement A). Here, CTNNB1 is linked to severe intellectual disability-progressive spastic diplegia syndrome.