Abstract: Objective To explore the clinical characteristics of autosomal dominant intellectual disability type 21(MRD21)related with CCCTC-binding factor(CTCF) mutations. Methods The clinical data of an outpatient with CTCF mutations, laboratory and genetic test results was retrospectively collected, and relevant literatures were reviewed. Results A 6-year-old male patient had feeding difficulties during the neonatal period and has experienced constipation since infancy. He has exhibited global developmental delay since early childhood, characterized by intellectual and language deficits, as well as autism-like behaviors. There is no history of epileptic seizures. Brain magnetic resonance imaging and electroencephalography findings were normal. Physical examination revealed poor eye contact, microcephaly and no facial dysmorphism. Whole exome sequencing confirmed by Sanger sequencing detected a de novel heterozygous mutation in CTCF: c.1087-2A＞G. His parents did not have this mutation. Conclusions The clinical manifestations of MRD21 lack specificity. Intellectual disability is the most frequent finding. Other presentations may also include microcephaly, digestive system symptoms like feeding difficulties and constipation, as well as behavioral abnormalities, which are also relatively common. Genetic testing aids in confirming the diagnosis.

Key words: intellectual disability, CCCTC binding factor(CTCF), microcephaly, feeding difficulty