Integrating Genetic, Clinical, and Histopathological Data for Definitive Diagnosis of PRKAG2-Related Disease

Background: PRKAG2-related disease is an autosomal dominant disorder caused by pathogenic variants in the PRKAG2 gene, leading to glycogen accumulation in cardiomyocytes. It is characterized by left ventricular hypertrophy (LVH), ventricular pre-excitation, and conduction disease. Due to the rarity of the condition and the frequent occurrence of private variants, functional or pathological testing is required for definitive pathogenicity classification. Case Presentation: We describe a 22-year-old male referred for evaluation after experiencing exertional dyspnea and a syncopal episode. Family history revealed sudden cardiac deaths and conduction disease requiring pacemaker implantation. The patient exhibited mild LVH on imaging, conduction abnormalities on electrophysiological study, and a heterozygous PRKAG2 variant (c.1643C>T; p.Ser548Leu), classified as likely pathogenic according to ACMG guidelines. Cascade screening identified the variant in three family members, one of whom exhibited a positive phenotype. Endomyocardial biopsy revealed glycogen accumulation, providing histopathological confirmation of PRKAG2-related disease. Conclusions: This case underscores the importance of integrating genetic, clinical, and histopathological data in variant interpretation. Endomyocardial biopsy can provide definitive evidence to reclassify a PRKAG2 variant as pathogenic, thereby guiding management and family screening.