Genetic Architecture of Pediatric Cardiomyopathies Assessed by Whole-Exome Sequencing: Insights Into Early-Onset and Syndromic Forms.

Pediatric cardiomyopathies (CM) are rare and heterogeneous heart disorders, including hypertrophic, dilated, restrictive, arrhythmogenic, and non-dilated CM. While their genetic basis is well characterized in adults, it remains less clearly defined in children particularly in early-onset apparently isolated and syndromic forms. We conducted a retrospective study (2018-2024) of 59 pediatric patients who underwent Whole-Exome Sequencing (WES) for CM at Amiens and Lille University Hospitals, aiming to characterize the genetic architecture of pediatric CM. WES identified at least one Variant Of Interest (VOI) in 62.7% of patients (37/59), including 45.8% (27/59) of P/LP variants, and 16.9% (10/59) of VUS. VOI identification yields for HCM and DCM were respectively 67.7% and 57.1%. Yield was higher in patients diagnosed before 1 year of age compared with those diagnosed later (72.7% vs. 56.7%). Variants were identified in classical CM genes, including sarcomeric genes, but also in less typical and syndromic genes. Among patients diagnosed before 6 months, 55% carried a variant in genes associated with syndromic cardiomyopathy, including cases with initially isolated cardiac phenotypes. These findings support the use of WES as a first-line approach in pediatric CM and highlight the contribution of complex and syndromic genetic architectures to early-onset and severe diseases.