Clinical Validity of Genes for Heritable Thoracic Aortic Aneurysm and Dissection

Genetic Testing in Inherited Heart Diseases

Inherited heart diseases include numerous conditions, from the more prevalent hypertrophic cardiomyopathy (HCM) and familial hypercholesterolaemia (FH), to the comparatively less common inherited arrhythmia syndromes, such as long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT) and Brugada syndrome (BrS). Genetic testing has evolved rapidly over the last decade and is now considered a mainstream component of clinical management of inherited heart diseases. Cardiac manifestations can also be part of wider syndromes, and genetic testing can play a critical role in clarifying the underlying aetiological basis of disease in some cases. The greatest utility of a genetic diagnosis, however, comes from the ability to elucidate disease risk amongst asymptomatic at-risk family members. Given the nuances and challenges, cardiac genetic testing is best performed in a multidisciplinary specialised clinic with access to cardiac genetic counselling.

Genetics and Precision Medicine: Heritable Thoracic Aortic Disease

Heritable thoracic aortic disease (HTAD) can have life-threatening consequences if not diagnosed early. Affected individuals and at-risk family members benefit from both cardiology and genetic evaluations, including genetic testing. Important information can be obtained through family history, medical history, and genetic testing to help guide management and assess risk. A genetic diagnosis can guide cardiovascular management (type and frequency of vascular imaging, timing of surgical intervention), risk assessment for arterial aneurysm/dissection, evaluation of nonvascular features, and familial testing.

A clinical scoring system for congenital contractural arachnodactyly

PURPOSE

Congenital contractural arachnodactyly (CCA) is an autosomal dominant connective tissue disorder manifesting joint contractures, arachnodactyly, crumpled ears, and kyphoscoliosis as main features. Due to its rarity, rather aspecific clinical presentation, and overlap with other conditions including Marfan syndrome, the diagnosis is challenging, but important for prognosis and clinical management. CCA is caused by pathogenic variants in FBN2, encoding fibrillin-2, but locus heterogeneity has been suggested. We designed a clinical scoring system and diagnostic criteria to support the diagnostic process and guide molecular genetic testing.

METHODS

In this retrospective study, we assessed 167 probands referred for FBN2 analysis and classified them into a FBN2-positive (n = 44) and FBN2-negative group (n = 123) following molecular analysis. We developed a 20-point weighted clinical scoring system based on the prevalence of ten main clinical characteristics of CCA in both groups.

RESULTS

The total score was significantly different between the groups (P < 0.001) and was indicative for classifying patients into unlikely CCA (total score <7) and likely CCA (total score ≥7) groups.

CONCLUSIONS

Our clinical score is helpful for clinical guidance for patients suspected to have CCA, and provides a quantitative tool for phenotyping in research settings.

SMAD4 rare variants in individuals and families with thoracic aortic aneurysms and dissections

SMAD4 pathogenic variants cause juvenile polyposis (JPS) and hereditary hemorrhagic telangiectasia (HHT), and 40% of affected individuals also have thoracic aortic disease. At the same time, SMAD4 pathogenic variants have not been reported in thoracic aortic disease families without JPS-HHT. A SMAD4 heterozygous variant, c.290G>T, p.(Arg97Leu), not present in population databases and predicted to be damaging to protein function, was identified in a family with thoracic aortic disease and no evidence of HHT or JPS. Cellular studies revealed that the SMAD4 p.(Arg97Leu) alteration increased SMAD4 ubiquitination and 26S proteasome-mediated protein degradation. Smooth muscle cells (SMCs) infected with lentivirus expressing the SMAD4 p.(Arg97Leu) variant demonstrated reduced contractile protein gene expression when compared to that of wild-type SMAD4. In addition, two rare variants were identified in individuals with early age of onset of thoracic aortic dissection. These results suggest that SMAD4 rare missense variants can lead to thoracic aortic disease in individuals who do not have JPS or HHT.

Genetic counselling and testing in adults with congenital heart disease: A consensus document of the ESC Working Group of Grown-Up Congenital Heart Disease, the ESC Working Group on Aorta and Peripheral Vascular Disease and the European Society of Human Genetics

Thanks to a better knowledge of the genetic causes of many diseases and an improvement in genetic testing techniques, genetics has gained an important role in the multidisciplinary approach to diagnosis and management of congenital heart disease and aortic pathology. With the introduction of strategies for precision medicine, it is expected that this will only increase further in the future. Because basic knowledge of the indications, the opportunities as well as the limitations of genetic testing is essential for correct application in clinical practice, this consensus document aims to give guidance to care-providers involved in the follow-up of adults with congenital heart defects and/or with hereditary aortic disease. This paper is the result of a collaboration between the ESC Working Group of Grown-Up Congenital Heart Disease, the ESC Working Group on Aorta and Peripheral Vascular Disease and the European Society of Human Genetics. Throughout the document, the importance of correct counseling in the process of genetic testing is emphasized, indications and timing for genetic studies are discussed as well as the technical modalities of genetic testing. Finally, the most important genetic diseases in adult congenital heart disease and aortic pathology are also discussed.

Clinical Implications of Identifying Pathogenic Variants in Individuals With Thoracic Aortic Dissection

BACKGROUND

Thoracic aortic dissection is an emergent life-threatening condition. Routine screening for genetic variants causing thoracic aortic dissection is not currently performed for patients or family members.

METHODS

We performed whole exome sequencing of 240 patients with thoracic aortic dissection (n=235) or rupture (n=5) and 258 controls matched for age, sex, and ancestry. Blinded to case-control status, we annotated variants in 11 genes for pathogenicity.

RESULTS

Twenty-four pathogenic variants in 6 genes (COL3A1, FBN1, LOX, PRKG1, SMAD3, and TGFBR2) were identified in 26 individuals, representing 10.8% of aortic cases and 0% of controls. Among dissection cases, we compared those with pathogenic variants to those without and found that pathogenic variant carriers had significantly earlier onset of dissection (41 versus 57 years), higher rates of root aneurysm (54% versus 30%), less hypertension (15% versus 57%), lower rates of smoking (19% versus 45%), and greater incidence of aortic disease in family members. Multivariable logistic regression showed that pathogenic variant carrier status was significantly associated with age <50 (odds ratio [OR], 5.5; 95% CI, 1.6-19.7), no history of hypertension (OR, 5.6; 95% CI, 1.4-22.3), and family history of aortic disease (mother: OR, 5.7; 95% CI, 1.4-22.3, siblings: OR, 5.1; 95% CI, 1.1-23.9, children: OR, 6.0; 95% CI, 1.4-26.7).

CONCLUSIONS

Clinical genetic testing of known hereditary thoracic aortic dissection genes should be considered in patients with a thoracic aortic dissection, followed by cascade screening of family members, especially in patients with age-of-onset <50 years, family history of thoracic aortic disease, and no history of hypertension.

NGS-Based genetic testing for heritable cardiovascular diseases. Specific requirements for obtaining informed consent

Clinical genetic testing in cardiovascular genetic medicine has undergone rapid changes. Next generation sequencing allows simultaneous testing of all genes associated with any cardiovascular phenotype, and molecular genetic testing for multiple genes has become the standard of practice for cardiovascular medicine. While technical and clinical advantages of multigenic approaches are evident, informed consent procedures have become more complex and challenging to the physician ordering such a test, particularly due to the increased potential for unsolicited findings. Based on the EuroGentest "Guidelines for diagnostic next-generation sequencing" we here propose a set of disease-specific requirements for obtaining informed consent for NGS-based genetic testing in a cardiogenetic clinic. We can show that it is often not feasible to obtain informed consent for every detail and suggest, in such cases, to reach general consent beforehand and discuss specific implications of unsolicited findings after the test results are available.

Developing a genomics rotation: Practical training around variant interpretation for genetic counseling students

With the wide adoption of next-generation sequencing (NGS)-based genetic tests, genetic counselors require increased familiarity with NGS technology, variant interpretation concepts, and variant assessment tools. The use of exome and genome sequencing in clinical care has expanded the reach and diversity of genetic testing. Regardless of the setting where genetic counselors are performing variant interpretation or reporting, most of them have learned these skills from colleagues, while on the job. Though traditional, lecture-based learning around these topics is important, there has been growing need for the inclusion of case-based, experiential training of genomics and variant interpretation for genetic counseling students, with the goal of creating a strong foundation in variant interpretation for new genetic counselors, regardless of what area of practice they enter. To address this need, we established a genomics and variant interpretation rotation for Stanford's genetic counseling training program. In response to changes in the genomics landscape, this has now evolved into three unique rotation experiences, each focused on variant interpretation in the context of various genomic settings, including clinical laboratory, research laboratory, and healthy genomic analysis studies. Here, we describe the goals and learning objectives that we have developed for these variant interpretation rotations, and illustrate how these concepts are applied in practice.