Hydrops Fetalis, Thickened Placenta and Other Sonographic Findings in a Low-Level Trisomy 21 Mosaicism: A Case Report

Abstract

We report a case of trisomy 21 mosaicism detected upon amniocentesis in a 36-year-old woman. Ultrasound examination at 23weeks’ gestation showed a fetus with hydrops, pulmonary hypoplasia, oligohydramnios, thickened placenta, and intrauterine growth retardation. Cytogenetic analysis revealed low-percentage (6%) mosaicism for trisomy 21. Hydrops fetalis and thickened placenta are uncommon findings in fetuses affected by trisomy 21 mosaicism. A short review of the literature is given regarding the sonographic findings associated with trisomy 21 mosaicism, and the genetic counseling in such cases.

Multicolor-FISH Characterization of a Prenatal Mosaicism for a Chromosomal Rearrangement Undetected by Molecular Cytogenetics

“…The use of CMA lowered the capacities of mosaic detection, and the sensitivity of this technique for both gains and losses is around 10% (9-15%) [Ballif et al, 2006;Carey et al, 2014]. The lowest level of prenatal mosaicism detected previously reported in the literature was 6% in a case of trisomy 21 (detected through karyotyping of amniocytes) [Sifakis et al, 2008].…”

Germinal and Somatic Trisomy 21 Mosaicism: How Common is it, What are the Implications for Individual Carriers and How Does it Come About?

“…A recent large-scale study has highlighted that current screening procedures are incapable of differentiating between fetuses with an apparently normal karyotype in relation to those shown to be T21 mosaics by conventional cytogenetic analysis of amniotic fluid cells [44]. It is also well known that DS cases that have been suspected to be T21 mosaics based on subtle clinical features, and where therefore a larger number of cells have been analyzed, show a large variation in proportion of T21 cells [45-49]. …”