Abstract: Objective To investigate the genetic etiology of a child with global developmental delay. Methods The clinical data and genetic testing results of a child with the global developmental delay caused by heterozygous variation of the TCF4 gene were reviewed. Results Full exome assays in the children did not reveal large deletion/duplication variants with definite pathogenicity associated with clinical symptoms of the subjects. The firstgeneration verification results showed the heterozygous variation of TCF4 gene c.1732C>T（p.R578C），which was a possibly pathogenic variation. Conclusion Conclusion The heterozygous variation of the TCF4 gene is closely related to global developmental delay；early intervention is effective in the treatment of global developmental delay caused by heterozygous variation of the TCF4 gene.

Key words: TCF4 gene, global developmental delay（GDD）, heterozygous mutations