TTN mutation-positive hypertrophic cardiomyopathy in congenitally corrected transposition of the great arteries: A rare coexistence.

Congenitally corrected transposition of the great arteries (CCTGA) is a rare congenital cardiac malformation, in which the morphologic right ventricle (RV) supports the systemic circulation. Systemic RV hypertrophy is usually secondary to pressure overload, while intrinsic myopathic hypertrophy due to sarcomeric gene mutation is exceedingly uncommon. We report a 37-year-old male who presented with exertional dyspnea and chest discomfort. Echocardiography and cardiac magnetic resonance (CMR) imaging revealed atrioventricular and ventriculoarterial discordance consistent with CCTGA, accompanied by asymmetric hypertrophy of the systemic RV and interventricular septum without significant outflow obstruction. Late gadolinium enhancement demonstrated patchy myocardial fibrosis. Genetic testing identified a heterozygous truncating variant in the TTN gene (exon 46, c. 14414del, p.Thr4805 LysfsTer24), confirming familial hypertrophic cardiomyopathy (HCM). The present case highlights an extremely rare coexistence of CCTGA and TTN-related HCM of the systemic RV. Recognition of this overlap requires high clinical suspicion, multimodal imaging, and molecular testing, which together enable accurate diagnosis, family counseling, and long-term management of this unique phenotype.