Chromosomal Microarray Analysis for the Fetuses with Aortic Arch Abnormalities and Normal Karyotype

Chromosomal Microarray Analysis in Fetuses Detected with Isolated Cardiovascular Malformation: A Multicenter Study, Systematic Review of the Literature and Meta-Analysis

Cardiovascular malformations (CVM) represent the most common structural anomalies, occurring in 0.7% of live births. The CVM prenatal suspicion should prompt an accurate investigation with fetal echocardiography and the assessment through genetic counseling and testing. In particular, chromosomal microarray analysis (CMA) allows the identification of copy number variations. We performed a systematic review and meta-analysis of the literature, studying the incremental diagnostic yield of CMA in fetal isolated CVM, scoring yields for each category of heart disease, with the aim of guiding genetic counseling and prenatal management. At the same time, we report 59 fetuses with isolated CVM with normal karyotype who underwent CMA. The incremental CMA diagnostic yield in fetuses with isolated CVM was 5.79% (CI 5.54–6.04), with conotruncal malformations showing the higher detection rate (15.93%). The yields for ventricular septal defects and aberrant right subclavian artery were the lowest (2.64% and 0.66%). Other CVM ranged from 4.42% to 6.67%. In the retrospective cohort, the diagnostic yield was consistent with literature data, with an overall CMA diagnostic yield of 3.38%. CMA in the prenatal setting was confirmed as a valuable tool for investigating the causes of fetal cardiovascular malformations.

Molecular Approaches in Fetal Malformations, Dynamic Anomalies and Soft Markers: Diagnostic Rates and Challenges-Systematic Review of the Literature and Meta-Analysis

Fetal malformations occur in 2-3% of pregnancies. They require invasive procedures for cytogenetics and molecular testing. "Structural anomalies" include non-transient anatomic alterations. "Soft markers" are often transient minor ultrasound findings. Anomalies not fitting these definitions are categorized as "dynamic". This meta-analysis aims to evaluate the diagnostic yield and the rates of variants of uncertain significance (VUSs) in fetuses undergoing molecular testing (chromosomal microarray (CMA), exome sequencing (ES), genome sequencing (WGS)) due to ultrasound findings. The CMA diagnostic yield was 2.15% in single soft markers (vs. 0.79% baseline risk), 3.44% in multiple soft markers, 3.66% in single structural anomalies and 8.57% in multiple structural anomalies. Rates for specific subcategories vary significantly. ES showed a diagnostic rate of 19.47%, reaching 27.47% in multiple structural anomalies. WGS data did not allow meta-analysis. In fetal structural anomalies, CMA is a first-tier test, but should be integrated with karyotype and parental segregations. In this class of fetuses, ES presents a very high incremental yield, with a significant VUSs burden, so we encourage its use in selected cases. Soft markers present heterogeneous CMA results from each other, some of them with risks comparable to structural anomalies, and would benefit from molecular analysis. The diagnostic rate of multiple soft markers poses a solid indication to CMA.

8q21.11 microdeletion syndrome: Delineation of HEY1 as a candidate gene in neurodevelopmental and cardiac defects

BACKGROUND

8q21.11 microdeletion syndrome is a rare chromosomal disorder characterized by recurrent dysmorphic features, a variable degree of intellectual disability and ocular, cardiac and hand/feet abnormalities. To date, ZFHX4 is the only candidate gene implicated in the ocular findings. In this study, we evaluated a patient with a de novo 8q21.13-21.3 deletion to define a new small region of overlap (SRO) for this entity.

METHODS

We conducted a clinical evaluation and comparative genomic hybridization (CGH) 4x44K microarrays in a patient with de novo unbalanced translocation t(8;16)(q21; q11.2).

RESULTS

The case, a 6-year-old boy, presented dysmorphic features including an elongated face, brachycephaly with a high forehead, an underdeveloped ala, thin upper lip, micrognathia, low-set ears, hypotonia, mild intellectual disability, cortical atrophy with thin corpus callosum defect, and an atrial septal defect. No ocular abnormalities were found. Microarray analysis revealed a 9.6 Mb interstitial 8q21.11-21.3 deletion, not including the ZFHX4 gene. This microdeletion was confirmed in our patient through qPCR analysis, and both parents had a normal profile. Alignment analysis of our case defined a new SRO encompassing five genes. Among them, the HEY1 gene is involved in the embryonic development of the heart, central nervous system, and vascular system. Hrt1/Hey1 null mice show perinatal lethality due to congenital malformations of the aortic arch and its branch arteries. HEY1 has also been linked to the maintenance of neural stem cells, inhibition of oligodendrocyte differentiation, and myelin gene expression.

CONCLUSION

HEY1 is a candidate gene for both neurological and cardiac features of the 8q21.11 microdeletion syndrome and might, therefore, explain specific components of its pathophysiology.

Associated Chromosomal Abnormalities in Fetuses Diagnosed Prenatally with Right Aortic Arch

Right aortic arch (RAA) is an abnormal embryologic development of the aorta characterized by its descendance on the right side of the trachea. This anomaly is accompanied often by other intracardiac and extracardiac anomalies and it is also known for potential association with genetic aberrations, most common being 22q11.2 deletion. The aim of the study was to evaluate the incidence of chromosomal anomalies and in particular 22q11.2 deletion in RAA. Moreover, we assessed the prognosis of fetuses with isolated RAA. Our second objective was to evaluate the prevalence of hypoplastic or absent thymus in RAA fetuses diagnosed with 22q11.2 deletion. We conducted a retrospective study of all fetuses with RAA over a period of 10 years diagnosed prenatally in a tertiary referral center in Romania. A detailed ultrasound was obtained in each case. We extracted the cases that were investigated genetically and selected the cases positive for 22q11.2 deletion. These fetuses were followed up until pregnancy termination or birth to confirm the ultrasound findings. Deletion 22q11.2 was present in 23.52% (4/17) cases. The incidence was particularly high when the fetuses presented a small thymus. In conclusion, we believe that all cases of RAA, including when isolated, should be referred for genetic testing and especially 22q11.2 deletion exclusion. Also, we suggest considering hypoplastic thymus to be a soft marker for this deletion.

Prenatal findings and pregnancy outcome in fetuses with right and double aortic arch. A 10-year experience at a tertiary center

OBJECTIVE

Our objective was to evaluate the accuracy of the prenatal diagnosis and the relation between the type of right aortic arch (RAA) with other intra- or extracardiac (EC) and chromosomal anomalies.

METHODS

A retrospective, observational study was conducted between 2011-2020 in a Romanian tertiary center. All RAA cases, including double aortic arch (DAA), were extracted from the databases and studied thoroughly.

RESULTS

We detected 18 RAA cases: five (27.78%) type I (mirror image, "V" type), 11 (61.12%) type II ("U" type), and two (11.10%) DAA cases. Heart anomalies were associated in 38.89% (overall), 60% (type I), 36.37% (type II), and 0% (DAA) cases. Tetralogy of Fallot represented the most prevalent cardiac malformation (in 22.23% of cases). EC anomalies were present in 44.44% of fetuses (20% of type I, 54.55% of type II, and 50% of DAA cases). Genetic abnormalities were found in 41.17% of pregnancies, with 22q11.2 deletion in 23.53%. 55.55% of the cases had a good neonatal evolution and 44.45% of the pregnancies were terminated. An overall good outcome of pregnancy was noted in 40% of type I RAA, 63.64% of type II RAA, and 50% of DAA cases. All RAA cases examined in the first trimester were correctly diagnosed.

CONCLUSIONS

RAA can be accurately diagnosed and classified by means of prenatal ultrasound since early pregnancy. A detailed anatomy scan and genetic testing, including 22q11 deletion, should be offered to all pregnancies when RAA is discovered. When isolated, RAA associates a good outcome, indifferently the anatomical type.