Reversible cardiac function and left ventricular hypertrophy in a Chinese man with mitochondrial myopathy: a case report

Abstract

Background: Mitochondrial myopathies (MMs) are a group of multi-system diseases caused by abnormalities in mitochondrial DNA (mtDNA) or mutations of nuclear DNA (nDNA). The diagnosis of mitochondrial myopathy (MM) is reliant on the combination of history and physical examination, muscle biopsy, histochemical studies, and next-generation sequencing. Patients with MMs have diverse clinical manifestations. In the contemporary literature, there is a paucity of reports on cardiac structure and function in this rare disease. We report a Chinese man with MM accompanied with both acute right heart failure and left ventricular hypertrophy.

Case presentation: A 49-year-old man presented with clinical features suggestive of MM, i.e., ophthalmoparesis, weakness of the pharyngeal and extremity muscles, and respiratory muscles which gradually progressed to respiratory insufficiency. He had a family history of mitochondrial myopathy. He had increased levels of serum creatine kinase and lactate. Muscle biopsy of left lateral thigh revealed 8% ragged red fibers (RRF) and 42% COX-negative fibers. Gene sequencing revealed a novel heterozygote TK2 variant (NM_001172644: c.584T>C, p.Leu195Pro) and another heterozygous variant (NM_004614.4:c.156+958G>A; rs1965661603) in the intron of TK2 gene. Based on these findings, we diagnosed the patient as a case of MM. Echocardiography revealed right heart enlargement, pulmonary hypertension, left ventricular hypertrophy, and thickening of the main pulmonary artery and its branches. The patient received non-invasive ventilation and coenzyme Q10 (CoQ10). The cardiac structure and function were restored at 1-month follow-up.

Conclusions: This is the first report of reversible cardiac function impairment and left ventricular hypertrophy in a case of adult-onset MM, nocturnal hypoxia is a potential mechanism for left ventricular hypertrophy in patients with MM.

Keywords: Heart failure; Left ventricular hypertrophy; Mitochondrial myopathy; Pulmonary artery hypertension; Respiratory failure.

Fig. 1

The pedigree of the patient: the index case is a family member, II-3.

Fig. 2

Pre-treatment echocardiography (A-D). Apical four-chamber view showing enlargement of right atrium (RA) and right ventricle (RV) (A); Short-axis view of the heart showing dilation of the main pulmonary artery (MPA) and its branches (B); Peak tricuspid regurgitation velocity by continuous Doppler, peak right ventricle–to–right atrial systolic pressure gradient is 51 mmHg (C); Left ventricle short-axial view showing symmetric slight thickening of the left ventricle (LV); LV end-diastolic wall thickness is 13 mm (D)

Fig. 3

A novel TK2 variant (NM_001172644: c.584T>C, p.Leu195Pro) was discovered in a patient with mitochondrial myopathy. Single nucleotide mutation detected by second generation gene sequencing

Fig. 4

Echocardiography of the patient after one month of treatment (A-D). Apical four-chamber view showing normal RA and RV (A); Short-axis view of the heart showing the normal main pulmonary artery (MPA) and its branches (B); Long axial section of LV showing the normal range of left atrial (LA) and LV size (C); Left ventricle short-axial view showing normal chamber wall thickness; LV end-diastolic wall thickness is 9 mm (D)