BACKGROUND Xia–Gibbs syndrome (XGS, OMIM: 615829), caused by mutations within the AT-Hook DNA-binding motif-containing protein 1 ( AHDC1 ) gene (OMIM: 615790), located on the short arm of chromosome 1 within the cytogenetic band 1p36.11, contains five noncoding 5 exons, a single 4.9-kb coding exon, and a noncoding 3 exon. CASE SUMMARY In this case report, we diagnosed and treated a 6-mo-old girl with XGS. The primary clinical symptoms included global developmental delay, hypotonia, and mild dysmorphic features. Using high-throughput whole-exosome sequencing to sequence the patient and her parents, and the results showed a novel frameshift mutation of c.1155dupG (p.Arg386Alafs*3) in the AHDC1 gene. The paternal gene was wild type. CONCLUSION This report extends the mutation spectrum of the AHDC1 gene to provide the diagnostic basis for genetic counseling in families with XGS.