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case_images: Serial chest radiography. Serial progression of cardiomegaly is observed. The presence of a dual-chamber pacemaker is noted.
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case_images: A chest radiography revealed that her heart size increased progressively over the past 2 years (Figure 1). Although common mutations known to cause dilated cardiomyopathy, such as those in TTN, LMNA, MYH7, and TNNT2, were not found in next-generation sequencing, the m.3243A > G heterozygote mutation of the MT-TL1 gene was confirmed by Sanger sequencing (see Supplementary material online, Figure S1).
case_images: Histologic findings of the myocardium of the right ventricle obtained by endomyocardial biopsy. (A) Haematoxylin and eosin staining: hypertrophy of myocytes (black arrows) is observed; (B) Electron microscopy: a disarrangement of mitochondrial cristae (red asterisks) is observed.
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case_images: Haematoxylin-eosin staining showed hypertrophy of myocytes (Figure 2A), and an electron microscopy revealed a disarrangement of mitochondrial cristae (Figure 2B), which were compatible with mitochondrial cardiomyopathy; Congo red staining was negative.