Diverse Clinical Spectrum of TTN-Truncation Variant Cardiomyopathy: A Case Series Illustrating Asymptomatic, Arrhythmic, Recurrent Takotsubo, and Inflammatory Phenotypes

Truncating variants in the TTN gene (TTNtv) are the most common genetic causes of dilated cardiomyopathy (DCM).Despite this high prevalence, the clinical spectrum of TTNtv-associated cardiomyopathy remains incompletely characterized, with variable penetrance, expressivity, and phenotypic manifestations.In this study, we present four cases of TTNtv cardiomyopathy illustrating diverse clinical presentations: an asymptomatic phenotype with moderate left ventricular systolic dysfunction discovered through screening, a severe arrhythmic phenotype with ventricular tachycardia storm requiring multiple ablations and implantable cardioverter-defibrillator (ICD) shocks, a recurrent stress-induced (takotsubo) presentation with two discrete episodes, which we present as a hypothesis-generating observation, and an inflammatory presentation with fluorodeoxyglucose-positron emission tomography (FDG-PET) evidence of active myocardial inflammation and symptomatic response to corticosteroids.These cases illustrate the potential clinical value of genetic testing, cardiac magnetic resonance imaging, and individualized assessment in TTNtv cardiomyopathy, and suggest that genetic counseling and cascade testing should be considered for affected individuals and their families.