Objective: To explore the genetic basis for a child with mentally retardation.
Methods: G-banding karyotyping, single nucleotide polymorphism array (SNP-array) and fluorescence in situ hybridization (FISH) were performed for the child. Karyotyping and FISH were also carried out for her parents.
Results: SNP-array has detected a 5077 kb microdeletion at 5q35.2q35.3 and a 4964 kb microduplication at 7q36.2q36.3 in the child. The results were confirmed by FISH. Based on above results, the father was subsequently found to carry a cryptic t(5;7) (q35.2; q36.2) translocation. The child was verified to have inherited a der(5) t(5;7)(q35.2; q36.2) from her father.
Conclusion: The 5077 kb microdeletion at 5q35.2q35.3 may have predisposed to the Sotos syndrome in the child. SNP-array combined with G-banding karyotyping and FISH can help to detect cryptic chromosomal translocations among patients.