Abstract 4134551: <i>Outstanding Research Award in Pediatric Cardiology:</i> Cardiomyopathy-Associated Pathogenic Variants in Pediatric Myocarditis: A Study from the Pediatric Cardiomyopathy Registry

Background: Recent studies have demonstrated that patients with myocarditis (MC) may have a higher burden of cardiomyopathy (CM)-associated gene variants than the general population. However, data in children is limited. The Pediatric Cardiomyopathy Registry (PCMR), a large multi-center registry of children with CM, includes patients with dilated CM (DCM) secondary to myocarditis (MC). Hypothesis: We hypothesized patients with DCM secondary to MC in the PCMR have a higher burden of CM-associated gene variants than healthy controls, and clinical genetic testing in this population is rare. Aims: We aimed to: (1) calculate the prevalence of pathogenic (P) or likely pathogenic (LP) CM-associated variants in patients with DCM secondary to MC and compare to the prevalence in heart-healthy controls and (2) report the rate of clinical genetic testing in this population. Methods: The PCMR was queried to identify patients with DCM secondary to MC who underwent exome sequencing as part of a prior prospective study at 14 sites in North America. Controls from the Indiana University Biobank were matched 4:1 with cases based on genomic similarity. A curated gene list was comprised of 46 genes associated with CM. A second gene list included 102 genes associated with CM or MC in the ClinVar database. The prevalence of variants was compared using Chi-Square or Fisher’s exact tests. Results: A total of 32 patients were identified with DCM secondary to MC. Median enrollment age was 1.5 years (IQR 0.4-10.3) and 53% were female. There was no family history in 88%. The prevalence of P/LP variants from the curated list was 34.4% in cases compared to 4.7% in controls (p&lt;0.001). The prevalence of P/LP variants from the ClinVar list was 31.3% in cases compared to 6.3% in controls (p&lt;0.001). Variants were identified in 8 genes: ABCC9, ANKRD1, MYH6, MYH7, MYPN, PLN, TPM1 and TTN. No P/LP variants were found in desmosomal genes. The prevalence of variants was higher but not significantly different in older children compared to infants (45.0% vs 16.6%, p=0.1). The prevalence of variants in MC was similar to previously reported rates in all causes of DCM (34.4% vs 28.8%, p=0.5). Only 22% of cases received clinical genetic testing. Conclusion: Approximately 1 in 3 children with DCM secondary to MC carry a CM-associated P/LP variant, which is significantly higher than the prevalence in healthy controls. Given the high prevalence, routine genetic testing should be considered in this population.