Prenatal detection of Trisomy 18q: Edwards syndrome

Abstract

Introduction: Most fetuses with trisomy 18 have an abnormal ultrasound results. Trisomy of the long arm of chromosome 18 is an important factor in the development of the phenotype of Edwards syndrome. Case report: A 28 year old woman, in 24th gestational week of her first pregnancy, was referred to our clinic for genetic counseling, after combined screening for aneuploidies in the first trimester of her pregnancy showed increased risk for trisomy 13 and 18, and fluorescent in situ hybridization (FISH) from amniotic fluid results were obtained only for chromosomes 13, 21 and sex chromosomes, showing euploid constitution, but for the chromosome 18 there were no findings. After careful analysis of the obtained results, geneticist suggested a thorough ultrasonography examination of the fetus that showed polyhydramnion, asymmetrical ventriculomegaly and agenesis of corpus callosum. Consequent cytogenetic analysis showed karyotype 46,XX,-13,+der(13),t(13;18)(p11;q11). Parents had normal karyotypes, so finding of trisomy 18q in fetus, is due to de novo translocation. After genetic counseling, on parents demand and after ethic committee approval, this pregnancy was terminated and autopsy revealed dysmorphic facial features (including triangular face, low-set ears, short palpebral fissures), clenched hands, ventriculomegaly, choroid plexus cysts, partial agenesis of corpus callosum, subaortic ventricular septum defect, bilateral, trilobate lungs and saccular stage of lung development. Conclusion: Karyotyping of fetuses with high risk for chromosomal disorders is necessary not only for the confirmation of clinical diagnosis, but also for a proper genetic counseling.

Keywords

• chromosome 18
• trisomy 18q
• fetal anomalies