Penetrance and disease expression of (likely) pathogenic variants associated with inherited cardiomyopathies in the general population

Background. (Likely) pathogenic variants associated with arrhythmogenic cardiomyopathy (ACM), dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) are recommended to be reported as secondary findings in genome sequencing studies. This provides opportunities for early diagnosis, but also fuels uncertainty in variant carriers (G+), since disease penetrance is incomplete. We assessed the prevalence and disease expression of G+ in the general population. Methods. We identified (likely) pathogenic variants associated with ACM, DCM and/or HCM in 200,643 UK Biobank individuals, who underwent whole exome sequencing. We calculated the prevalence of G+ and analysed the frequency of cardiomyopathy/heart failure diagnosis. In undiagnosed individuals, we analysed early signs of disease expression. Results. We found a prevalence of 1:578, 1:251 and 1:149 for (likely) pathogenic variants associated with ACM, DCM and HCM respectively. Compared to controls, cardiovascular mortality was higher in DCM G+ (OR 1.67 [95% CI 1.04;2.59], p=0.030), but similar in ACM and HCM G+ (p≥0.100). More specifically, cardiomyopathy or heart failure diagnosis were more frequent in DCM G+ (OR 3.66 [95% CI 2.24;5.81], p=4.9×10-7) and HCM G+ (OR 3.03 [95% CI 1.98;4.56], p=5.8×10-7), but comparable in ACM G+ (p=0.172). In contrast, ACM G+ had more ventricular arrhythmias (p=3.3×10-4). In undiagnosed individuals, left ventricular ejection fraction was reduced in DCM G+ (p=0.009). Conclusions. In the general population, (likely) pathogenic variants associated with ACM, DCM or HCM are not uncommon. Although G+ have increased mortality and morbidity, disease expression in these carriers from the general population remains low. Decisions on application of cascade screening and frequency of cardiological examination should be based on multiple factors, such as the variant and disease expression.

Double heterozygous familial hypercholesterolaemia: Case series, genetics and Cascade screening of families

Background: Familial hypercholesterolemia (FH) is an autosomal dominant disorder of lipoprotein metabolism characterized by high levels of LDL-cholesterol (LDL-C) in the blood. Studies identified more than 1,000 mutations of the LDLR gene in FH patients with incidence rates between 1: 500 and 1: 300. The mutation that occurs primarily in: LDLR, apoB, PCSK9, LDLRAP1 genes, 80% of which were detected the LDLR gene mutation. Nowaday, FH disease has not been paid much attention, leading to a delay in treatment. Objectives: identify mutations in other family members of the patient FH. Subjects and Methods: 14 family members of FH patients were gene analyzed, identified mutations on exons 4, 9 LDLR genes. Results: 11/15 family members carrying heterozygous mutations on exon 4 and exon 9 of LDLR gene. Patient and 1 family member detected and treated late, leading to complications of myocardial infarction. Conclusion: Therefore, Cascade screening of patient's family members has an important role in early detection, genetic counseling and treatment, even in cases where pedigree members do not have xanthomas and no increase or slight increase in blood lipids. This is the basis for early counseling and treatment for members with mutations, reducing the risk of coronary artery diseases in the future.

Histopathological Features and Protein Markers of Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a heritable heart muscle disease characterized by syncope, palpitations, ventricular arrhythmias and sudden cardiac death (SCD) especially in young individuals. It is estimated to affect 1:5,000 individuals in the general population, with >60% of patients bearing one or more mutations in genes coding for desmosomal proteins. Desmosomes are intercellular adhesion junctions, which in cardiac myocytes reside within the intercalated disks (IDs), the areas of mechanical and electrical cell-cell coupling. Histologically, ACM is characterized by fibrofatty replacement of cardiac myocytes predominantly in the right ventricular free wall though left ventricular and biventricular forms have also been described. The disease is characterized by age-related progression, vast phenotypic manifestation and incomplete penetrance, making proband diagnosis and risk stratification of family members particularly challenging. Key protein redistribution at the IDs may represent a specific diagnostic marker but its applicability is still limited by the need for a myocardial sample. Specific markers of ACM in surrogate tissues, such as the blood and the buccal epithelium, may represent a non-invasive, safe and inexpensive alternative for diagnosis and cascade screening. In this review, we shall cover the most relevant biomarkers so far reported and discuss their potential impact on the diagnosis, prognosis and management of ACM.

A Case Report of Genetic Cascade Screening in Dilated Cardio-myopathy: A Perspective for Preventive Cardiology

Cardiomyopathies are heterogeneous and critical disorders of cardiovascular diseases. One of the most common inherited cardiomyopathies is DCM (dilated cardiomyopathy). Genetic disorders are found in approximately 50% of DCM cases. We aimed to describe a case of DCM in a 42-year-old woman in 2018 at Farhud Genetic Clinic, Tehran, Iran. To detect genetic involvement, Next-generation sequencing (NGS) was performed and the data were evaluated carefully. Variations in different genes coding crucial proteins in cardiac muscle structure (i.e. Titin, Obscurin, MYH6, and LAMA4) and proteins involved in channels (i.e. CAVNA1C, SCN1B and SCN5A) were detected by whole-exome sequencing (WES). In agreement with the clinical manifestations and molecular analysis, DCM was confirmed. This study provides further evidence on the diagnostic role of NGS in borderline DCM cases. It also shows the recently developed high throughput sequencing can provide clinicians with this approach to diagnosis, treatment, and prevention of such hard-to-diagnose disorders. Furthermore, this study highlights the basis of personalized medicine, namely detection of high-risk individuals by revealing some genetic variants as predictive risk factors, and initial prevention of DCM.

Experience in genetic testing of hypertrophic cardiomyopathy using nanopore DNA sequencing

Aim. To investigate the application of the Oxford Nanopore Technologies’ third generation sequencing for the genetic testing of hypertrophic cardiomyopathy.Material and methods. The study involved 12 patients with hypertrophic cardiomyopathy aged 18 to 67 years (women, 9; men, 3). Using the PCR barcoding amplicons (SQK-LSK109) protocol, DNA libraries were created which contained long-range PCR fragments of the MYH7, MYBPC3, TNNT2, TNNI3 and TPM1 genes. The sequencing was performed using the MinION system by Oxford Nanopore Technologies (UK). Bioinformatic algorithms for data analysis included Guppy v.5.0.7, Nanopolish and Clairvoyante. The identified genetic variants were confirmed by Sanger sequencing.Results. Data on the complete sequence of the five major sarcomeric genes for hypertrophic cardiomyopathy were obtained. We found eight potentially disease-causing sequence variants in MYH7, MYBPC3 and TNNT2 genes by monomolecular sequencing. However, only three mutations p.Arg243Cys, p.Tyr609Asn, p.Arg870His in the MYH7 gene, and one mutation p.Lys985Asn in the MYBPC3 were confirmed by Sanger sequencing. Cascade screening of pathogenic variant p.Arg870His in the MYH7 gene was performed. We found one asymptomatic carrier.Conclusion. It appears that monomolecular sequencing technology is a feasible approach to identify mutations in patients with hypertrophic cardiomyopathy. Although improvement in accuracy of DNA sequencing, as well as optimization and simplification of bioinformatic algorithms for identification of the genetic variants are needed.

Hypercholesterolemia in children and adolescents: focus on the familial variant

Familial hypercholesterolemia is characterized by a significant increase in serum low-density lipoprotein cholesterol concentration, which even in the absence of other risk factors leads to the development of atherosclerotic vascular lesions beginning in childhood. With significant prevalence in the population, familial hypercholesterolemia is rarely diagnosed in time due to the Long absence of clinical manifestations. Today the urgent task is to develop and implement programs of primary detection of familial hypercholesterolemia in children and adolescents. Early detection of patients with familial hypercholesterolemia and timely initiation of adequate lipid-lowering therapy will curb the rate of atherosclerosis progression, which will significantly reduce disability and mortality from cardiovascular diseases in older age groups. There are four types of screening: cascade, targeted, opportunistic and universal. Cascade screening is currently considered the most effective and cost-effective way to identify new patients with familial hypercholesterolemia among relatives of an index patient, the patient with the established diagnosis. Targeted screening is based on searching for individuals with familial hypercholesterolemia among groups of patients with the early development of atherosclerotic vascular lesions, for example, in cardiology or neurology hospitals. Opportunistic screening is a non-systematic, sporadic determination of cholesterol levels in patients seeking medical care for any reason. It is most applicable in primary care health care settings. Universal screening is a mass screening of certain age groups and is a highly effective way of early diagnosis, especially in combination with reverse cascade screening of parents, siblings, and other relatives of the index patient. Implementation of programs of early childhood detection of familial hypercholesterolemia, setting up systems of adequate routing of patients, timely prescription of effective lipid-lowering therapy will contribute to health preservation and prolongation of working age, development, and preservation of labor potential of the country.

Cascade screening for beta-thalassaemia in Pakistan: relatives’ experiences of a decision support intervention in routine practice

Low uptake of cascade screening for βeta-thalassaemia major (β-TM) in the ‘Punjab Thalassaemia Prevention Project’ (PTPP) in Pakistan led to the development of a ‘decision support intervention for relatives’ (DeSIRe). This paper presents the experiences of relatives of children with β-TM of the DeSIRe following its use by PTPP field officers (FOs) in routine clinical practice. Fifty-four semi-structured qualitative interviews were conducted (April to June 2021) with relatives in seven cities in the Punjab province (Lahore, Sheikhupura, Nankana Sahab, Kasur, Gujranwala, Multan and Faisalabad). Thematic analysis shows that participants were satisfied with the content of the DeSIRe and its delivery by the FOs in a family meeting. They understood that the main purpose of the DeSIRe was to improve their knowledge of β-TM and its inheritance, and to enable them to make decisions about thalassaemia carrier testing, particularly before marriage. Participants also raised concerns about the stigma of testing positive; however, they believed the DeSIRe was an appropriate intervention, which supported relatives to make informed decisions. Our findings show that the DeSIRe is appropriate for use by healthcare professionals in routine practice in a low-middle income country, and has the potential to facilitate shared decision making about cascade screening for thalassaemia. Further research is needed to prove the efficacy of the DeSIRe.

Dilated cardiomyopathy: the role of genetics, highlighted in a family with Filamin C (FLNC) variant

Dilated cardiomyopathy (DCM) is a heterogenous group of disorders characterised by left ventricular dilatation and dysfunction, in the absence of factors affecting loading conditions such as hypertension or valvular disease, or significant coronary artery disease. The prevalence of idiopathic DCM is estimated between 1:250 and 1:500 individuals. Determining the aetiology of DCM can be challenging, particularly when evaluating an individual and index case with no classical history or investigations pointing towards an obvious acquired cause, or no clinical clues in the family history to suggest a genetic cause. We present a family affected by DCM associated with Filamin C variant, causing sudden cardiac death at a young age and heart failure due to severe left ventricular impairment and myocardial scarring. We review the diagnosis and treatment of DCM, its genetic associations and potential acquired causes. Thorough assessment is mandatory to risk stratify and identify patients who may benefit from primary prevention implantable cardioverter defibrillator therapy according to international guidelines. Genetic testing has some limitations, and is positive in only 20%–35% of DCM, but should be considered in specific cases to identify families who may benefit from cascade screening after appropriate counselling. The management of often complex familial cardiomyopathy requires specialist input for every case, and the appropriate infrastructure to coordinate investigations.

Bicuspid Aortic Valve: Genetic and Clinical Insights

Bicuspid aortic valve (BAV) is the most common valvular congenital heart disease, with a prevalence of 0.5 to 2% in the general population. Patients with BAV are at risk for developing cardiovascular complications, some of which are life-threatening. BAV has a wide spectrum of clinical presentations, ranging from silent malformation to severe and even fatal cardiac events. Despite the significant burden on both the patients and the health systems, data are limited regarding pathophysiology, risk factors, and genetics. Family studies indicate that BAV is highly heritable, with autosomal dominant inheritance, incomplete penetrance, variable expressivity, and male predominance. Owing to its complex genetic model, including high genetic heterogenicity, only a few genes were identified in association with BAV, while the majority of BAV genetics remains obscure. Here, we review the different forms of BAV and the current data regarding its genetics. Given the clear heritably of BAV with the potential high impact on clinical outcome, the clinical value and cost effectiveness of cascade screening are discussed.