A foetus with 18p11.32-q21.2 duplication and Xp22.33-p11.1 deletion derived from a maternal reciprocal translocation t(X;18)(q13;q21.3).

ABSTRACT

BACKGROUND: Non-invasive prenatal testing (NIPT) evaluates circulating cell-free DNA (cfDNA) and has been widely applied, with highly accurate results for detecting foetal trisomies 21, 18 and 13. Recently, increasing attention has been paid to the clinical application of the non-invasive detection of foetal sub-chromosomal duplications and deletions beyond common aneuploidies. CASE PRESENTATION A 32-year-old healthy pregnant woman was referred to the Medical Genetic Centre of Ganzhou Maternal and Child Health Care Hospital. As routine practice, ultrasound examination at a gestational age of 16 weeks showed that the foetus is normal. To avoid invasive prenatal diagnosis procedures, an NIPT was offered to further screen for common foetal chromosomal abnormalities. The result showed that there was an approximately 50.94 Mb duplication in p11.32-q21.2 of chromosome 18 and an approximately 58.46 Mb deletion in p22.33-p11.1 of chromosome X. In addition, the chromosome karyotypes of the parents and foetus were also analysed. Chromosome karyotype analysis results showed that foetal karyotype was 46,X,der(18), the maternal karyotype was 46,XX,t(X;18)(q13;q21.3), and the paternal karyotype revealed no obvious abnormality. CONCLUSION: In this case, we successfully detected a healthy pregnant woman with balanced translocation X;18(q13;q21.3) and described the foetal karyotype as 46,X,der(18)t(X;18)(q11;q21.1)mat. Our report illustrated these cases which present complex X;autosome balance translocation and X;autosome unbalance translocation which may contribute to severe clinical phenotypes. In addition, our report also proved that the interruption of genes in the Xq critical region is not only reason of primary infertility. Finally, we prompted that NIPT might play a role in the first trimester screening of sub-chromosomal rearrangement.