Prenatal diagnosis of a de novo supernumerary marker derived from chromosome 16.

Marker chromosomes are supernumerary chromosomes of unknown origin and are seldom found in prenatal diagnosis. Application of fluorescent in situ hybridization (FISH) allows the identification of the chromosomal origin of markers. Estimation of the risk of an abnormal phenotype outcome can be enabled by collecting data on phenotypes associated with markers of the same chromosomal origin. So far only very few cases of prenatal diagnosis of de novo supernumerary markers derived from chromosome 16 have been reported. Here the prenatal diagnosis of a de novo supernumerary marker chromosome 16 is described and the relevant literature discussed.

Prenatal diagnosis of a de novo inversion of chromosome (2)(p21q11).

Prenatal diagnosis of "apparently balanced" chromosomal rearrangements, if not inherited from a parent, are problematic for genetic counsellors and families. Although the parents need to be informed about the increased risk of multiple congenital anomalies, the anomalies that the fetus is at risk can not be discussed unless a similar breakpoint and accompanying phenotype have been reported in the literature. In the reported case prenatal ultrasound examination revealed a massive hydrocephalus internus and IUGR. The karyotype of the fetus was inv(2)(p21q11) de novo. Postmortem examination revealed short palpebral fissures, hypertelorism, atypical nasiolabial configuration, microgenia, extended position of the fingers, atypical proximal inserted first toe, hydrocephalus internus, hypoplasia of the cerebellum and bulbi olfactorii, bilateral hypoplastic lungs, atrial septal defect II, small right ventricle, dysplasia of the pulmonary valve, hypoplastic pulmonary artery, right proximal ureterostenosis, hypoplastic gall bladder. This is the first description of a de novo inversion (2)(p21q11) in a fetus with multiple malformations.

Prenatal diagnosis of a supernumerary aberrant chromosome 9.

For counselling of parents, as well as to basically understand how chromosome aneuploidies affect embryonic or fetal development, it is of great importance to analyse and collect genotypes of fetuses with clinical anomalies. This report describes the first prenatal diagnosis of a supernumerary chromosome 9 with deletion of the chromosome region 9q34. Ultrasound examination in the 13th week of gestation detected increased nuchal translucency of 6.9 mm, fetal ascites and a pronounced facial anomaly. Hysteroscopic examination before curettage made it possible to describe this facial anomaly as a double-sided, median defect of the superior lip with protrusion of parts of intersegments. This report provides evidence that the absence of trisomy 9 in 9q34 does not prevent abnormal facial development.