Histopathology of ventricular sections obtained from the proband.

<p>(<b>A</b>) Cross section of ventricular myocardium shows hypertrophied myocytes with profound intracellular vacuolation and marked variation in the nucleus size (hematoxylin and eosin staining, original magnification × 400). (<b>B</b>) Myocardial fibers in longitudinal section shows loss of the normal parallel arrangement, increased side-branching, and frequent side-to-side branches connections (hematoxylin and eosin staining, original magnification × 400). (<b>C</b>) Masson’s trichrome staining shows increased interstitial fibrosis with blue color (original magnification × 400). (<b>D</b>) Electron microscopy shows angulated myofibrillar with length-heterogeneity sarcomere lengths and excess mitochondria (bar = 5 µm). (<b>E</b>) Granular glycogen accumulation in the subsarcolemmal regions of cardiac myocytes (bar = 0.5 µm). (<b>F</b>) Myofibrillar dissolution and widening of intermyofibrillar spaces in which scattered glycogen granules and mitochondria are seen (bar = 2 µm). G, Prominent interstitial fibrosis and myofibrillar disarray (bar = 2 µm).