Congenital cardiac abnormalities in monozygotic twins. Report and review of the literature

In Utero Diagnoses of Strikingly Similar Presentations of Complete Atrioventricular Septal Defects in a Pair of Dizygotic Twins Concordant for Trisomy 21

Trisomy 21, or Down syndrome (DS), is a genetic disorder affecting approximately 1 in 500–750 live births. The prevalence of DS has increased over the past two decades, correlating with a rise in the proportion of pregnancies complicated by advanced maternal age. There is also a correlation between advanced maternal age and dizygotic twinning rates. There is an increased risk of at least one twin being affected in dizygotic pregnancies compared to singletons. However, despite this greater relative risk, reports of concordance of DS in both dizygotic twins are very rare. Congenital heart disease (CHD) occurs in roughly 40% of individuals with DS, but there can be considerable phenotypic variation. The most common, atrioventricular septal defect accounts for only 40% of CHD seen in DS. There is also a higher incidence of CHD in twins, but also with a low incidence of concordance. There have been only five reported cases of concordant DS in dizygotic twins with confirmed chromosomal analyses; none of which describe concordant congenital heart disease. Here, we describe an unusual case of dizygotic twins of differing genders concordant for both Down syndrome and congenital heart disease of a strikingly similar presentation.

Role of connexins in human congenital heart disease: the chicken and egg problem

Inborn cardiac diseases are among the most frequent congenital anomalies and are the main cause of death in infants within the first year of age in industrialized countries when not adequately treated. They can be divided into simple and complex cardiac malformations. The former ones, for instance atrial and ventricular septal defects, valvular or subvalvular stenosis or insufficiency account for up to 80% of cardiac abnormalities. The latter ones, for example transposition of the great vessels, Tetralogy of Fallot or Shone’s anomaly often do not involve only the heart, but also the great vessels and although occurring less frequently, these severe cardiac malformations will become symptomatic within the first months of age and have a high risk of mortality if the patients remain untreated. In the last decade, there is increasing evidence that cardiac gap junction proteins, the connexins (Cx), might have an impact on cardiac anomalies. In the heart, mainly three of them (Cx40, Cx43, and Cx45) are differentially expressed with regard to temporal organogenesis and to their spatial distribution in the heart. These proteins, forming gap junction channels, are most important for a normal electrical conduction and coordinated synchronous heart muscle contraction and also for the normal embryonic development of the heart. Animal and also some human studies revealed that at least in some cardiac malformations alterations in certain gap junction proteins are present but until today no particular gap junction mutation could be assigned to a specific cardiac anomaly. As gap junctions have often been supposed to transmit growth and differentiation signals from cell to cell it is reasonable to assume that they are somehow involved in misdirected growth present in many inborn heart diseases playing a primary or contributory role. This review addresses the potentional role of gap junctions in the development of inborn heart anomalies like the conotruncal heart defects.

A novel variation of PLAGL1 in Chinese patients with isolated ventricular septal defect

AIMS

Ventricular septal defect (VSD) is the most common congenital heart disease (CHD). A number of genetic studies have linked the gene of PLAGL1 to the etiology of CHD. The present study aimed to identify potential pathogenic mutations for PLAGL1 and to provide insights into the etiology of isolated VSD.

METHODS

Case-control mutational analysis was performed in 300 patients with isolated VSD and 300 healthy controls. Two protein-coding extons of PLAGL1 and their partial flanking intron sequences were amplified by polymerase chain reaction and sequenced on an ABI3730 Automated Sequencer. CLC workbench software was used to compare the conservatism of PLAGL1 protein with other multiple species.

RESULTS

Neither missense nor frame-shift mutations were detected in two protein-coding extons of PLAGL1. But a novel synonymous variation (c.486A>G, p. E162E) was detected in protein-coding exon-2. The glutamic that translated with the mutational codon is conservative when compared with other species.

CONCLUSIONS

We detected a synonymous variation in the protein-coding exon-2 of PLAGL1 in isolated VSD patients. It is possible that the etiology of isolated VSD might not be directly linked with this mutation, but might be associated with other patterns of gene expression regulation in PLAGL1, such as in the methylation-dependent manner.

Twin-twin transfusion syndrome, coarctation of the aorta and hypoplastic aortic arch: a case series report

AIM

The twin-twin transfusion syndrome (TTTS) complicates 10-30% of monochorionic pregnancies. The incidence of pulmonary stenosis and endocardial fibroelastosis is especially high in the recipient twin. We report a novel finding of four cases of coarctation of the aorta and hypoplastic aortic arch in the donor to raise awareness of cardiac lesions in twins affected by TTTS.

METHOD

Retrospective review of both neonatal database and mortality data from 2002 to 2007 with cross-validation from the local tertiary cardiology unit data (1998-2006) to identify children presenting with coarctation who were also twins.

RESULTS

We identified four monochorionic twin pairs affected by the TTTS, delivered between 25 weeks and 36 weeks' gestation, where the donor was found to have coarctation of the aorta or a hypoplastic aortic arch. In addition, two of the four recipients also had cardiac abnormalities. There was a high mortality rate of 30% for both twins, and a high morbidity rate, especially for neurological sequelae.

CONCLUSION

We believe that the types of abnormalities seen may be explained by the altered fetal blood flow and haemodynamics in TTTS. Given the increased prevalence of congenital heart disease in TTTS, with an increased risk of coarctation in the donor twin and pulmonary stenosis in the recipient, intra-uterine surveillance and a post-natal comprehensive cardiac assessment for both twins is warranted.

Aortic valvular atresia. Associated cardiovascular anomalies

The pathological anatomy of 109 specimens of aortic valvular atresia was reviewed for the purpose of identifying the cardiovascular anomalies associated with that condition. We found the most commonly associated anomaly to be coarctation of the aorta, which was present in 71 percent of our cases and judged to be hemodynamic significance in one-third of the involved cases. Other associated anomalies, in order of decreasing frequency, were mitral atresia, anomalous systemic and pulmonary venous connections, abnormalities of branching of the aortic arch, and ventricular septal defect. The study demonstrated that aortic atresia is associated with a significant incidence of other cardiovascular anomalies. Additional anomalies, when present, may complicate emerging attempts at surgical correction of this condition.

Coarctation of the aorta in dizygotic twins

The incidence of congenital heart disease is higher in monozygotic than dizygotic twins, with a higher concordance rate. Although coarctation of the aorta has previously been reported in monozygotic twins, to the best of our knowledge it has not been described in dizygotic twins. We report here such a concurrence in dizygotic twins conceived by in-vitro fertilisation. The finding provides support for both genetic and environmental factors in the aetiology of congenital heart disease. Furthermore, it highlights our lack of data regarding the outcome of in-vitro fertilisation.

Dizygotic twins concordant for truncus arteriosus

Persistent truncus arteriosus (TA) is an uncommon congenital cardiovascular malformation, which comprises between 0.4% and 4% of all congenital heart defects. Occurrence of TA in siblings has been reported infrequently. Twins concordant for isolated TA appear to have been reported only once previously. In this paper, we describe dizygotic twin females who were concordant for isolated TA.