[Analysis of a child with mental retardation due to a de novo variant of the KAT6A gene].

Objective: To explore the genetic etiology for a child featuring mental retardation and speech delay.

Methods: Clinical data of the child was collected. DNA was extracted from peripheral blood samples of the child and members of his pedigree. Whole exome sequencing was carried out for the child, and candidate variants were verified by Sanger sequencing. Prenatal diagnosis was provided for his mother upon her subsequent pregnancy.

Results: The child has mainly featured mental retardation, speech delay, ptosis, strabismus, photophobia, hyperactivity, and irritability. Whole exome sequencing revealed that he has harbored a pathogenic heterozygous variant of the KAT6A gene, namely c.5314dupA (p.Ser1772fs*20), which was not detected in either of his parents. The child was diagnosed with Arboleda-Tham syndrome. The child was also found to harbor a hemizygous c.56T>G (p.Leu19Trp) variant of the AIFM1 gene, for which his mother was heterozygous and his phenotypically normal maternal grandfather was hemizygous. Pathogenicity was excluded. Prenatal diagnosis has excluded the c.5314dupA variant of the KAT6A gene in the fetus.

Conclusion: The heterozygous c.5314dupA (p.Ser1772fs*20) variant of the KAT6A gene probably underlay the Arboleda-Tham syndrome in this child. Above finding has enabled genetic counseling and prenatal diagnosis for this pedigree.