Multinational experience with next-generation sequencing: opportunity to identify transthyretin cardiac amyloidosis
Sandra Marques E Silva1, Andrea Virginia Ferreira Chaves2,3,4, Murillo Antunes5,6
1GEDORAC/DCC/SBC-Study Group on Rare Diseases with Cardiac Impairment from Brazilian Society of Cardiology, Hospital de Base do Distrito Federal (HBDF), Brasilia, Brazil.
Insights
A 17-gene next-generation sequencing panel effectively identified genetic causes of hypertrophic cardiomyopathy (HCM) and phenocopies in patients with unexplained left ventricular hypertrophy. This genetic testing is crucial for diagnosing treatable conditions like transthyretin cardiac amyloidosis and Fabry disease.
Area of Science:
- Genetics
- Cardiology
- Molecular Diagnostics
Background:
- Sarcomeric hypertrophic cardiomyopathy (HCM) requires differentiation from similar conditions due to differing prognoses and management strategies.
- Unexplained left ventricular hypertrophy necessitates early genetic diagnosis via predictive or diagnostic testing.
- Identifying transthyretin cardiac amyloidosis (ATTR-CA) and Fabry disease (FD) is critical due to available targeted therapies.
Purpose of the Study:
- To assess the feasibility and practicality of a 17-gene next-generation sequencing (NGS) panel for detecting common genetic causes of HCM and HCM phenocopies.
- To determine the detection rates of pathogenic variants associated with HCM and treatable phenocopies.
- To highlight the importance of diagnosing ATTR-CA and FD for timely therapeutic intervention.
Main Methods:
- An international, multicenter, cross-sectional pilot study analyzed peripheral dried blood spot samples from patients with unexplained left ventricular wall thickness (LVWT) ≥13 mm.
- Next-generation sequencing (NGS) was performed at a central laboratory to detect variants in 17 genes, including splice and flanking regions.
- Illumina NextSeq 500 and NovaSeq 6000 sequencing systems were utilized for variant detection.
Main Results:
- Out of 535 samples, 128 (23.9%) showed pathogenic/likely pathogenic variants for HCM or its phenocopies.
- A total of 132 variants (24.7% diagnostic yield) were detected, with 115 (21.5%) linked to HCM and 17 (3.2%) to phenocopies.
- The most frequent HCM variants were in MYH7 (11.2%) and MYBPC3 (7.7%). Phenocopy variants included TTR (1.3%) and GLA (0.4%), associated with ATTR-CA and FD, respectively.
Conclusions:
- The 24.7% diagnostic yield confirms the strategy's effectiveness in identifying common HCM forms and phenocopies across diverse geographic locations.
- The study emphasizes the clinical significance of including ATTR-CA (TTR variants) and FD (GLA variants) in the differential diagnosis for unexplained LVWT.
- Early diagnosis of these treatable genetic disorders through comprehensive genetic screening can improve patient outcomes.
Background:
Sarcomeric hypertrophic cardiomyopathy (HCM) must be differentiated from phenotypically similar conditions because clinical management and prognosis may greatly differ. Patients with unexplained left ventricular hypertrophy require an early, confirmed genetic diagnosis through diagnostic or predictive genetic testing. We tested the feasibility and practicality of the application of a 17-gene next-generation sequencing (NGS) panel to detect the most common genetic causes of HCM and HCM phenocopies, including treatable phenocopies, and report detection rates. Identification of transthyretin cardiac amyloidosis (ATTR-CA) and Fabry disease (FD) is essential because of the availability of disease-specific therapy. Early initiation of these treatments may lead to better clinical outcomes.
Methods:
In this international, multicenter, cross-sectional pilot study, peripheral dried blood spot samples from patients of cardiology clinics with an unexplained increased left ventricular wall thickness (LVWT) of ≥13 mm in one or more left ventricular myocardial segments (measured by imaging methods) were analyzed at a central laboratory. NGS included the detection of known splice regions and flanking regions of 17 genes using the Illumina NextSeq 500 and NovaSeq 6000 sequencing systems.
Results:
Samples for NGS screening were collected between May 2019 and October 2020 at cardiology clinics in Colombia, Brazil, Mexico, Turkey, Israel, and Saudi Arabia. Out of 535 samples, 128 (23.9%) samples tested positive for pathogenic/likely pathogenic genetic variants associated with HCM or HCM phenocopies with double pathogenic/likely pathogenic variants detected in four samples. Among the 132 (24.7%) detected variants, 115 (21.5%) variants were associated with HCM and 17 (3.2%) variants with HCM phenocopies. Variants in MYH7 (n=60, 11.2%) and MYBPC3 (n=41, 7.7%) were the most common HCM variants. The HCM phenocopy variants included variants in the TTR (n=7, 1.3%) and GLA (n=2, 0.4%) genes. The mean (standard deviation) ages of patients with HCM or HCM phenocopy variants, including TTR and GLA variants, were 42.8 (17.9), 54.6 (17.0), and 69.0 (1.4) years, respectively.
Conclusions:
The overall diagnostic yield of 24.7% indicates that the screening strategy effectively identified the most common forms of HCM and HCM phenocopies among geographically dispersed patients. The results underscore the importance of including ATTR-CA (TTR variants) and FD (GLA variants), which are treatable disorders, in the differential diagnosis of patients with increased LVWT of unknown etiology.
