Pathogenic Variants Associated With Dilated Cardiomyopathy Predict Outcome in Pediatric Myocarditis

BACKGROUND

Myocarditis is one of the most common causes leading to heart failure in children and a possible genetic background has been postulated. We sought to characterize the clinical and genetic characteristics in patients with myocarditis ≤18 years of age to predict outcome.

METHODS

A cohort of 42 patients (Genetics in Pediatric Myocarditis) with biopsy-proven myocarditis underwent genetic testing with targeted panel sequencing of cardiomyopathy-associated genes. Genetics in Pediatric Myocarditis patients were divided into subgroups according to the phenotype of dilated cardiomyopathy (DCM) at presentation, resulting in 22 patients without DCM (myocarditis without phenotype of DCM) and 20 patients with DCM (myocarditis with phenotype of DCM).

RESULTS

Myocarditis with phenotype of DCM patients (median age 1.4 years) were younger than myocarditis without phenotype of DCM patients (median age 16.1 years; P<0.001) and were corresponding to heart failure-like and coronary syndrome-like phenotypes, respectively. At least one likely pathogenic/pathogenic variant was identified in 9 out of 42 patients (22%), 8 of them were heterozygous, and 7 out of 9 were in myocarditis with phenotype of DCM. Likely pathogenic/pathogenic variants were found in genes validated for primary DCM (BAG3, DSP, LMNA, MYH7, TNNI3, TNNT2, and TTN). Rare variant enrichment analysis revealed significant accumulation of high-impact disease variants in myocarditis with phenotype of DCM versus healthy individuals (P=0.0003). Event-free survival was lower (P=0.008) in myocarditis with phenotype of DCM patients compared with myocarditis without phenotype of DCM and primary DCM.

CONCLUSIONS

We report heterozygous likely pathogenic/pathogenic variants in biopsy-proven pediatric myocarditis. Myocarditis patients with DCM phenotype were characterized by early-onset heart failure, significant enrichment of likely pathogenic/pathogenic variants, and poor outcome. These phenotype-specific and age group-specific findings will be useful for personalized management of these patients. Genetic evaluation in children newly diagnosed with myocarditis and DCM phenotype is warranted.

Peripartum cardiomyopathy: the value of endomyocardial biopsy in diagnosis, prognostication, and therapy

We describe the case of a 21-year-old black female who was readmitted postpartum because of increasing exertional dyspnea, orthopnea, pleuritic chest pain, and pedal edema. The patient underwent a successful course of clinical treatment for peripartum cardiomyopathy consisting of a regimen of digoxin, diuretics, captopril, and heparin. The results of an endomyocardial biopsy done at readmission were normal: there was no evidence of inflammation, necrosis, or fibrosis; the endocardium, intramural arterioles, mitochondria, and ultrastructure were normal, as was the amount of glycogen; nuclear chromatin were evenly dispersed; and no antibodies were found. Previous studies have shown that approximately half of patients who suffer from peripartum cardiomyopathy recover, while half develop a more severe form of dilated cardiomyopathy. We venture to speculate that normal endomyocardial biopsy findings during the acute stage of the disease may be predictive of recovery. With more certainty, we propose that histologic findings from material taken during an acute episode can and should guide the course of therapy.