Concordance for bilateral congenital diaphragmatic hernia in a monozygotic dichorionic twin pair - first clinical report

Copy number detection in discordant monozygotic twins of Congenital Diaphragmatic Hernia (CDH) and Esophageal Atresia (EA) cohorts

The occurrence of phenotypic differences between monozygotic (MZ) twins is commonly attributed to environmental factors, assuming that MZ twins have a complete identical genetic make-up. Yet, recently several lines of evidence showed that both genetic and epigenetic factors could have a role in phenotypic discordance after all. A high occurrence of copy number variation (CNV) differences was observed within MZ twin pairs discordant for Parkinson's disease, thereby stressing on the importance of post-zygotic mutations as disease-predisposing events. In this study, the prevalence of discrepant CNVs was analyzed in discordant MZ twins of the Esophageal Atresia (EA) and Congenital Diaphragmatic Hernia (CDH) cohort in the Netherlands. Blood-derived DNA from 11 pairs (7 EA and 4 CDH) was screened using high-resolution SNP arrays. Results showed an identical copy number profile in each twin pair. Mosaic chromosome gain or losses could not be detected either with a detection threshold of 20%. Some of the germ-line structural events demonstrated in five out of eleven twin pairs could function as a susceptible genetic background. For example, the 177-Kb loss of chromosome 10q26 in CDH pair-3 harbors the TCF7L2 gene (Tcf4 protein), which is implicated in the regulation of muscle fiber type development and maturation. In conclusion, discrepant CNVs are not a common cause of twin discordancy in these investigated congenital anomaly cohorts.

Ductus Venosus: A Love Story of 14 Years

Ductus venosus is a tiny vessel with a central role in fetal circulation. Combining B-mode with color and pulsed Doppler is feasible to identify this vessel and evaluate the blood flow waveform at 11 to 13 weeks. The higher prevalence of abnormal A-wave in fetuses with abnormal karyotype and/or cardiac defects turned DV evaluation into a useful marker for chromosomal abnormalities and cardiopathies. Even when combined with nuchal translucency (NT) or biochemical markers, DV blood flow evaluation contributes to an increase in sensitivity and reduces false-positive rate. Abnormal ductal flow is also related to a worse fetal and perinatal outcome. In monochorionic twin pregnancies, in addition to NT measurement at 11 to 14 weeks, the Doppler assessment of DV blood flow increases relevantly the performance of screening for those at higher risk of developing twin-to-twin transfusion syndrome. This story of 14 years surely contributed to change the way first trimester screening is being implemented.