ARID1B and Intellectual disability: Nicolaides-Baraitser syndrome (NCBRS) has a similar phenotype to CSS and can be kept as a differential diagnosis. CSS was first reported and discovered by Evelyn Siris and Grange S. Coffin in the year 1970 [1-2]. ARID1B-related disorder (ARID1B-RD) results from pathogenic heterozygous variants in the ARID1B gene, which can manifest as classic CSS and intellectual disability, with or without nonspecific dysmorphic features.