Background: Conventional G-band karyotyping offers low-resolution detection of chromosome abnormalities and cannot provide information about the involved genomic content. On the other hand, array comparative genomic hybridization can offer a rapid and comprehensive detection of genomewide gains and losses with higher resolution, thus providing the genetic basis for prenatal diagnosis of fetal abnormalities.
Case presentation: A 35-year-old primigravid underwent cordocentesis at 28 weeks gestation due to the presence of polyhydramnios, intrauterine growth retardation, persistent right umbilical vein and mild stenosis of aortic arch at the ultrasound scan. Conventional G-band chromosome analysis revealed an apparently normal karyotype whereas the array CGH detected a de novo 8.97 Mb deletion at chromosome 11q22.3 → q23.3 and offered a precise characterization of the genetic defect.
Conclusions: The array CGH detected a de novo interstitial 11q deletion with its precise location and size which could be missed or confused by G-band chromosome analysis. The breakpoint was close to the folate sensitive rare fragile site FRA11B and the aphidicolin inducible common fragile site FRA11G, the co-localization fragile site could have caused instability and constitutional chromosomal breakage. This case study indicates that array CGH is a useful technique for detecting small unbalanced chromosomal abnormalities and should be an integral part of prenatal diagnosis for fetal malformations.
Keywords: Array CGH; Chromosome 11q deletion; FRA11B; FRA11G; Fragile sites; G-band karyotyping.