Different Clinical Presentation and Tissue Characterization in a Monozygotic Twin Pair with MYH7 Mutation-Related Hypertrophic Cardiomyopathy.

This case report demonstrates a pair of monozygotic twins with hypertrophic cardiomyopathy (HCM) carrying the same pathogenic mutation of MYH7 (p.G768R; c.2302G>A), detected by whole exome and Sanger genetic sequencing methods. On multi-modality imaging, they were reported to have similar, but not identical, morphologic expression. Particularly, the clinical presentation and tissue characteristics were not the same. Late gadolinium enhancement (LGE) and T1 mapping of cardiac magnetic resonance showed different extents of myocardial fibrotic characteristics in the twins (twin A: 16.3% LGE and 32.6% extracellular volume [ECV] of the whole left ventricle; twin B: 5.4% LGE and 28.1% ECV of the whole left ventricle). This extraordinary case of HCM provides evidence on the complex pathophysiological mechanisms of HCM and suggests the likely impact of epigenetics and environmental factors on HCM phenotype.