Case Report: Restrictive cardiomyopathy due to a rare mutation in troponin I gene (TNNI3) in a patient

Abstract

Background: Restrictive cardiomyopathy (RCM) is a rare cardiomyopathy often characterized by normal or reduced ventricular chamber volume and bi-atrial enlargement, caused mainly by mutations in the myonodal gene. It has a low incidence, non-specific clinical manifestations, rapid progression, and lack of specific treatment, with heart transplantation usually being the ultimate treatment.

Methods and results: This case reports a case of a 2-year-2-month-old boy located in Yunnan Province, China, who was admitted to the hospital with a 2-month history of orofacial bruising, aggravated by a 1-week history of bilateral eyelid swelling. After admission, electrocardiogram showed bi-atrial enlargement, echocardiography suggested bi-atrial enlargement with right and left ventricular diastolic hypoplasia, and cardiac magnetic resonance showed bi-atrial dilatation and possible localized myocardial fibrosis. A de novo heterozygous mutation (c.574C > T, p.Arg192Cys) in the TNNI3 gene was identified by whole exome sequencing and verified by Sanger sequencing. The patient's family opted for conservative treatment after diagnosis, but the patient died suddenly 2 months after diagnosis.

Conclusion: This study identified a case of RCM due to TNNI3 mutation, emphasizing the importance of cardiac MRI and genetic testing in the clinical diagnosis of RCM and the need for heart transplantation. The study also revealed the possible heterogeneity of TNNI3 mutations across ethnic and geographic backgrounds, suggesting that long-term studies of genetic mutations should be strengthened in the future to promote the development of precision treatment strategies for cardiomyopathy.

Keywords: TNNI3gene; case; children; mutation; restrictive cardiomyopathy.

Figure 1

Electrocardiogram showing bi-atrial enlargement with lower and anterior wall ST-segment depression.

Figure 2

(a) echocardiography showed bi-atrial enlargement, left atrium diameter 37 mm × 51.1 mm, right atrium diameter 31.5 mm × 35.4 mm, right and left ventricular diastolic hypoplasia, normal septal and ventricular wall thickness, and trace pericardial effusion; the ratio of the peak E and peak A velocities of mitral inflow (E/A) was 2.05. The mitral inflow was 2.05%, and the peak A velocity was 2.05%. (b) The cardiac magnetic resonance four-chamber view of the heart shows bi-atrial enlargement and ventricular narrowing, and gadolinium-delayed enhancement in both chambers of the heart shows suspicious striations.

Figure 3

Family tree of the first witness (black fill). Circles: female, squares: male.