Prenatal diagnosis of a de novo small supernumerary marker chromosome 16

In about 0.05% of newborn children, small supernumerary marker chromosomes (sSMC) are detected. The majority of these sSMC is proven to be de novo. The clinical outcome of an sSMC is difficult to predict as they can have different phenotypic consequences because of differences in the euchromatic content of DNA, differences in the degree of mosaicism or existence of an uniparental disomy (UPD) of the chromosomes homologous to the sSMC. We report here on the prenatal detection of a small supernumerary marker chromosome from chromosome 16. Prenatal cytogenetic analysis of cultured amniocytes was performed at week 1…