Cardiogenetics

Myocarditis is a complex inflammatory myocardial disease. Although traditionally regarded as exclusively immune-mediated, recent evidence highlights the significant role of underlying genetics on susceptibility, phenotypic variability, and long-term prognosis. This narrative review examines the evolving genetic architecture of myocarditis and its relationship to inherited cardiomyopathies, integrating mechanistic insights from molecular, imaging, and clinical studies. Variants in desmosomal genes such as desmoplakin (DSP) and plakophilin-2 (PKP2) are increasingly linked to recurrent myocarditis that may evolve into arrhythmogenic cardiomyopathy, supporting the concept of a genetically predisposed myocardium in which inflammatory stressors can act as triggers. Truncating variants in titin (TTN) and Filamin C (FLNC) are associated with fulminant or dilated phenotypes. Conversely, mutations in Lamin A/C (LMNA), Desmin (DES), and BCL2-Associated Athanogene 3 (BAG3) contribute to inflammatory myocardial remodeling and other forms of inherited cardiomyopathies. These findings collectively have the potential to redefine myocarditis as an inflammatory disorder influenced by genetic factors. Furthermore, advancements in genetic testing and multi-omics approaches show promise in enhancing diagnostic accuracy and informing management strategies.

Mitral annular disjunction (MAD) is associated with an increased risk of ventricular arrhythmias and sudden cardiac death, yet its genetic background remains poorly defined. We report the case of a 50-year-old man with MAD who survived cardiac arrest and carries three variants of unknown significance (VUS) in genes involved in cardiomyopathy pathogenesis. To explore the genetic basis of non-syndromic MAD, we performed a systematic review of the literature, identifying five case reports and one retrospective cohort study. The case reports described patients with MAD harboring four pathogenic variants and ten VUS. Two pathogenic variants were linked to cardiomyopathies, involving proteins of the nuclear envelope and cytoskeleton, while two were associated with channelopathies. The retrospective cohort study identified a recurrent variant in a gene involved in intercellular adhesion segregating within a family affected by MAD. Overall, available evidence suggests that genetic factors may hypothetically modulate susceptibility to MAD, not only in connective tissue disorders but also in isolated mitral valve disease. Variants associated with arrhythmogenic cardiomyopathies and channelopathies appear to cluster in families with non-syndromic MAD and arrhythmic phenotypes, suggesting a role in the arrhythmic substrate. However, in absence of definitive functional, segregation, or longitudinal data, the contribution of genetic variants to MAD should be interpreted with caution. Further genomic studies are needed to clarify their genetic contribution and prognostic implications.

Background: PRKAG2 cardiac syndrome is a rare autosomal dominant glycogen-storage cardiomyopathy that mimics sarcomeric hypertrophic cardiomyopathy (HCM) but features ventricular pre-excitation, progressive conduction disease and concentric hypertrophy due to intracellular glycogen accumulation. The c.905G>A (p.Arg302Gln) variant is one of the most frequently reported pathogenic substitutions. Case summary: We describe a three-generation family carrying the heterozygous PRKAG2 p.Arg302Gln variant. The proband, a 41-year-old man, presented with paroxysmal atrial fibrillation, short PR interval and abnormal intraventricular conduction associated with concentric left ventricular hypertrophy and preserved ejection fraction. Holter monitoring disclosed episodes of high-grade atrioventricular block, prompting implantation of a primary-prevention dual-chamber ICD. Two gene-positive brothers exhibited milder hypertrophy but shared sinus bradycardia, ventricular pre-excitation and supraventricular arrhythmias; one underwent catheter ablation of a posteroseptal accessory pathway. The affected mother displayed a hypertrophic phenotype complicated by sick sinus syndrome and permanent atypical atrial flutter requiring pacemaker implantation. No relevant extracardiac involvement was detected in any family member. Review and novelty: Using this family as a starting point, we provide a concise narrative review of PRKAG2 syndrome with emphasis on the Arg302Gln genotype, molecular mechanisms and emerging treatment strategies. We highlight key multimodality imaging and tissue-characterization features that help distinguish diffuse, concentric glycogen-storage hypertrophy from the often-asymmetric pattern of sarcomeric HCM. Integration of our findings with published Arg302Gln cohorts illustrates the broad phenotypic variability in conduction disease, pre-excitation and atrial arrhythmias. Conclusions: PRKAG2 p.Arg302Gln-related cardiomyopathy should be suspected in patients with otherwise unexplained left ventricular hypertrophy associated with short PR interval, pre-excitation or early brady–tachy arrhythmias. Early recognition of red-flag features, systematic genetic testing, family screening and tailored arrhythmia/device management are crucial, while emerging gene- and pathway-targeted therapies may offer future disease-modifying potential.