Myocardial energy impairment in MT-TI m.4300A > G mitochondrial cardiomyopathy with multisystem involvement

A 48-year-old man with a prior diagnosis of vitiligo presented with a 2-year history of intermittent chest tightness and mild exertional dyspnoea, accompanied by occasional tinnitus. His family history (Panel A) revealed clinically stable myocardial hypertrophy in his mother. Laboratory evaluation showed persistently elevated troponin I and N-terminal pro-B-type natriuretic peptide levels. Electrocardiography fulfilled voltage criteria for left ventricular hypertrophy (LVH) with inferolateral ST-segment and T-wave abnormalities. Cardiovascular magnetic resonance (CMR) demonstrated non-obstructive LVH with asymmetric geometry, left ventricular dilatation, and a preserved ejection fraction of 62% (Panel B). The diagnostic turning point was contrast-enhanced CMR, which revealed extensive late gadolinium enhancement (LGE) with mid-wall septal and patchy left ventricular free-wall involvement (arrows, Panel C). These regions showed concordant increases in T2, native T1, and extracellular volume (ECV), indicating myocardial oedema and fibrosis predominantly confined to LGE-positive areas (arrows, Panel D)—a pattern highly suggestive of mitochondrial cardiomyopathy and distinct from typical sarcomeric hypertrophy.