MBD5 protein contains a PWWP (pro-trp-trp-pro) domain, thought to be important in cell division, growth and differentiation.16, 17 Mutations in MBD5 are thought to be important in the clinical phenotype of 2q23.1 deletion syndrome,18, 19 where subjects with a deletion in this region of chromosome 2 show intellectual disability and autistic-like features. The gene discussed is MBD5; the disease is Intellectual disability.