A man in his 40s with a 20-year history of bilateral sensorineural hearing loss was referred for evaluation of left ventricular hypertrophy detected by echocardiography, which was performed because of high QRS voltage on a routine electrocardiogram with a strain pattern in the precordial leads. Neurological examination showed mild cognitive impairment, poor coordination, and muscle weakness of the bilateral lower limbs.
The transthoracic echocardiogram (parasternal long-axis and short-axis view) showed diffuse hypertrophy, moderately decreased contractility of the left ventricle, and increased intramyocardial signal intensisty.
Further evaluation included brain magnetic resonance imaging (MRI) demonstrating cerebellar atrophy and cardiac MRI demonstrating diffuse biventricular hypertrophy and moderately impaired left ventricular systolic function. A wide range of nodular and band-shaped late gadolinium enhancement was detected in the middle and epicardial layers of the left ventricular myocardium.
The constellation of short stature, sensorineural deafness, and mild cognitive impairment in addition to significant cardiac hypertrophy suggested the possibility of mitochondrial disease. Further investigation with sequencing of mitochondrial DNA from cutaneous fibroblasts revealed a 3243A>G point mitochondrial DNA variant, confirming the diagnosis of mitochondrial cardiomyopathy. Subsequent endomyocardial biopsy revealed mitochondrial hyperplasia and morphological abnormalities of cristae. The patient has been asymptomatic while undergoing therapy with a β-blocker, an angiotensin-converting enzyme inhibitor, and a mineralocorticoid receptor antagonist.
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