Prenatal diagnosis and genetic counseling of a uniparental isodisomy of chromosome 8 with no phenotypic abnormalities

BACKGROUND: Uniparental disomy (UPD) refers to an epigenomic abnormality in which both copies of, or a part of, a homologous pair of chromosomes are inherited from one parent. UPD arises via a number of mechanisms, including monosomic and trisomic rescue (in embryonic development), incomplete segregation of chromosomes, and mitotic recombination. CASE PRESENTATION: A 34-year-old, gravida 2, para 0 woman underwent amniocentesis at 18 weeks of gestation because the noninvasive prenatal testing (NIPT) showed the highly possibility of trisomy chromosome 8. GTG-banding karyotype analysis was performed on cultured amniocytes. Chromosomal microarray analysis (CMA), fluorescence in situ hybridization(FISH), whole-exome sequencing(WES) on uncultured amniocytes were performed. RESULTS: CMA detected a 29.4 Mb uniparental isodisomy of chromosome 8, arr 8p23.3p12(168484_29427840) × 2 hmz [GRCh37(hg19)]. FISH, WES and ultrasound examination showed no abnormal. At the 36-month checkup, the baby was developing normally. CONCLUSION: Combination of NIPT,prenatal ultrasound, karyotype analysis, CMA, FISH, WES and genetic counseling will prove a more accurate risk assessment for the prenatal diagnosis of UPD.