Objective: To explore the genetic cause for a child featuring developmental delay and mental retardation.
Methods: The child was analyzed with G-banded karyotyping and an Illumina Human CytoSNP-12 Beadchip.
Results: The father of the patient had a normal karyotype. The mother had a karyotype of 46, XX, t(12;15)(p13.3;q13). The child had a karyotype of 45, XY, der(12)t(12;15)(p13.3;q13)mat, -15. SNP array analysis showed that the child has deletions in 12p13.31-p13.33 and 15q11.2-q13.2. But no deletion or duplication was detected in his mother.
Conclusion: The unbalanced translocation involving chromosomes 12 and 15 probably accounts for the mental retardation in the child. SNP array is useful for the detection of chromosomal rearrangements and genetic counseling.