[Improved identification for trisomy 9p and partial trisomy 6q presented in a patient by array-based comparative genomic hybridization].

OBJECTIVE: To analyze the genetic cause for a child with growth retardation and mental retardation and discuss the application of array-based comparative genomic hybridization (aCGH) in its molecular genetic diagnosis.

METHODS: Conventional karyotyping of peripheral blood for the family was carried out. aCGH was performed to further ascertain the size and origin of the additional chromosome fragments.

RESULTS: In the trio family here, the karyotype of the father was normal, the karyotype of the mother was 46,XX, t(6;9)(q26;q21)and the proband child's was 47,XX,+der(9)?t(6;9)(q26;q21). aCGH showed that the extra chromosomal fragments originated from chromosome 9p24.3-q21.13 and the size was 78.26 Mb, and the repeat region included the 9p trisomy's clinical area. At the same time, it was confirmed that 6q26-q27 was trisomic and the fragment that related to development delay was 6.6 Mb. We determined that the proband's karyotype was 47,XX,+der(9)t(6;9)(q26;q21.13)mat finally.

CONCLUSION: The patient's abnormal chromosome has originated from her mother with balance translocation. The duplications of 9p24.3-q21.13 and 6q26-q27 may lead to growth retardation and mental retardation. Accompanied with the cytogenetic methods, aCGH can accurately identify the origin and size of the abnormal chromosomes, contributing to the genetic analysis.