Role of Whole-exome Sequencing in Phenotype Classification and Clinical Treatment of Pediatric Restrictive Cardiomyopathy

BACKGROUND Restrictive cardiomyopathy (RCM) is the least common cardiomyopathy in which the walls are rigid and the heart is restricted from stretching and filling properly. Cardiac troponin I (cTnI) mutation-caused myofibril Ca2+ hypersensitivity has been shown to be associated with impaired diastolic function. This study aimed to investigate the linkage between the genotype and clinical therapy of RCM. METHODS Five sporadic pediatric RCM patients confirmed by echocardiography were enrolled in this study. Whole-exome sequencing (WES) was performed for the cohort to find out candidate causative gene variants. Sanger sequencing confirmed the WES-identified variants. RESULTS TNNI3 variants were found in all of the five patients. R192H mutation was shared in four patients while R204H mutation was found only in one patient. Structure investigation showed that the C terminus of TNNI3 was flexible and mutation on the C terminus was possible to cause the RCM. Catechins were prescribed for the five patients once genotype was confirmed. Ventricular diastolic function was improved in three patients during the follow-up. CONCLUSIONS Our data demonstrated that TNNI3 mutation-induced RCM1 is the most common type of pediatric RCM in this study. In addition, WES is a reliable approach to identify likely pathogenic genes of RCM and might be useful for the guidance of clinical treatment scheme.