Objective: To explore the genetic basis for a child with mental retardation.
Methods: The child was subjected to chromosomal microarray analysis (CMA) and targeted capture next-generation sequencing for the exons of genes related to genetic and metabolic diseases. Candidate variants were verified by Sanger sequencing of the child and his parents.
Results: CMA suggested that the child has a 47,XYY karyotype. Next-generation sequencing revealed that the child has harbored compound heterozygous variants of the AUH gene, including c.677G>A (p.R226H) and c.373C>T (p.R125W), which were respectively inherited from his parents. Based on the American college of Medical Genetics and Genomics (ACMG) standards and guidelines, the c.677G>A (P.r226h) variant was predicted as variant of uncertain significance (PM2+PP4+PP3), whilst the c.373C>T (P.R125W) variant was predicted as likely pathogenic (PM1+PM2+PP3+PP4).
Conclusion: The child had XYY syndrome in conjunct with 3-methylglutaenedioic aciduria type I due to biallelic pathogenic variants of the AUH gene.