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    Case Report Series: Genetic and clinical characterization of long QT syndrome in admixed Ecuadorian patients and its implications for sudden cardiac death risk
    Long QT syndrome (LQTS) is a hereditary cardiac channelopathy associated with delayed ventricular repolarization and increased risk of life-threatening arrhythmias and sudden cardiac death. We report three Ecuadorian patients with LQTS, each presenting distinct clinical features and carrying pathogenic or likely pathogenic variants in KCNH2 or KCNQ1. Subject A, an 18-year-old woman with exertion-related syncope and a QTc of 520 ms, was diagnosed with LQT2 due to a KCNH2 p.Ala614Val variant. Subject B, a 3-year-old girl with congenital deafness and a QTc of 580 ms, was diagnosed with Jervell and Lange-Nielsen syndrome (JLNS), harboring a homozygous KCNQ1 p.Arg192Cys variant. Subject C, a 44-year-old man with recurrent syncope misdiagnosed as epilepsy and a strong family history of sudden death, was found to carry a KCNH2 p.Val612Met variant and had a QTc of 600 ms. All variants were classified according to ACMG/AMP guidelines and supported by in silico and functional data. Ancestry analysis provided additional genomic context in this admixed population. These cases underscore the clinical utility of integrating ECG findings, genetic testing, and ancestry-informed interpretation to improve diagnostic accuracy and personalize management in patients with inherited arrhythmia syndromes.
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    Case Report: Genomic and clinical insights into MYBPC3-related hypertrophic cardiomyopathy in Ecuadorian patients: implications for sudden cardiac death risk
    Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease and a leading cause of sudden cardiac death (SCD) in young adults and athletes. It exhibits marked clinical variability, which may be influenced by genetic background and environmental factors. Although MYBPC3 is the most frequently implicated gene, data from Latin American and admixed populations remain scarce. In this study, we describe three unrelated Ecuadorian patients with clinically diagnosed HCM who harbored MYBPC3 variants. Two patients carried likely pathogenic mutations (p.Glu258Lys and p.His875Profs*8), while novel missense variants (p.Ala536Pro and p.Thr274Met) were identified as variants of uncertain significance (VUS). Additional variants were detected in TTN, MYLK2, RYR1, SDHA, APOB, and JPH2, but given their classification as VUS or a lack of association with HCM, they are described only as incidental findings. An ancestry analysis revealed heterogeneous contributions of Native American, European, and African backgrounds, reflecting the admixed composition of the Ecuadorian population. This case series underscores the phenotypic heterogeneity of HCM, even among patients with MYBPC3 variants, and highlights the importance of genomic testing in underrepresented populations to improve diagnosis, family screening, and SCD risk stratification. 2026 Paz-Cruz, Guevara-Ramírez, Tamayo-Trujillo, Ruiz-Pozo, Cadena-Ullauri, Ibarra-Castillo, Laso-Bayas, Meza-Chico, Cabrera-Andrade and Zambrano.
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    Population Admixture and APOB Variant Landscape in Ecuadorian Mestizo Patients with Cardiac Diseases: Potential Implications for Familial Hypercholesterolemia Genetics
    Apolipoprotein B (APOB) is a key structural component of atherogenic lipoproteins and one of the principal genes implicated in familial hypercholesterolemia (FH). However, APOB genetic variation remains poorly characterized in Latin American and admixed populations. In this study, we performed a descriptive analysis of APOB variants in 60 Ecuadorian mestizo patients with inherited cardiac conditions using next-generation sequencing (NGS) and genetic ancestry inference. A total of 227 APOB variants were identified, the majority of which were classified as benign (n = 220) or likely benign (n = 3) according to ACMG criteria, while three variants were classified as variants of uncertain significance (VUS). The most frequently observed variants included rs1042034, rs679899, rs676210, and rs1367117. Comparative allele-frequency analyses using ALFA and PAGE Latin American reference datasets demonstrated that the APOB variant frequencies observed in the cohort were comparable to those reported in other Latin American populations, reflecting the admixed genetic background of Ecuadorian mestizos, predominantly of Native American and European ancestry. No pathogenic APOB variants were detected. Although lipid measurements were not available and genotype–phenotype associations could not be assessed, this study provides the first comprehensive overview of APOB variation in Ecuadorian mestizo individuals. These findings expand population-specific genomic data for an underrepresented group and underscore the importance of regional reference datasets for accurate variant interpretation in admixed populations.
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    The genomic bases of atrial fibrillation in an Ecuadorian patient: a case report
    Atrial fibrillation (AF) is one of the most globally prevalent arrhythmias with multifactorial factors, including environmental and genetic predisposition influences. The present case report describes a 30-year-old Ecuadorian mestizo male diagnosed with persistent AF with an history of hyperthyroidism, later progressing to hypothyroidism post-radioactive iodine therapy. Genomic test identified variants of uncertain significance in the TTN, MYH11, and RAF1 genes, which are associated with cardiovascular diseases but not directly linked to AF. The interplay between thyrotoxicosis and genetic predispositions is discussed as a potential mechanism underlying AF development. This report emphasizes the need for genomic screening and personalized strategies in populations like Ecuador with complex genetic and environmental backgrounds. 2025 Tamayo-Trujillo, Guevara-Ramirez, Meza-Chico, Cadena-Ullauri, Ruiz-Pozo, Paz-Cruz, Laso-Bayas, Ibarra-Castillo and Zambrano.