Objective: To explore the genetic cause for a boy featuring mainly with mental retardation.
Methods: G-banding karyotyping and fluorescence in situ hybridization (FISH) were carried out for the child and his parents. The child was also analyzed with chromosome microarray (CMA). Suspected microdeletion was validated with quantitative PCR.
Results: The proband was found to have a 47,XYY karyotype by both chromosome and FISH analyses, while both of his parents had a normal karyotype. CMA suggested that the proband had one copy of X chromosome and two copies of Y chromosome. In addition, CMA has also detected deletion of the KYNU gene (mapped at 2q22.2), which could be pathogenic. The result was confirmed by qPCR.
Conclusion: For its high resolution, CMA can be used to identify potential microdeletion/duplications among children with chromosome aneuploidy and unusual phenotypes.