A high proportion of children with severe cardiomyopathies show both myocarditis and genetic predispositions

AIMS: Severe cardiomyopathies in children may often demand a treatment with inclusion of mechanical circulatory support (MCS) or heart transplantation (HTx). Although these cardiomyopathies are not always hereditary, myocarditis may be regarded as a likely cause, if clinical course is not chronic. The aims of the study were to determine the genetic profile and prevalence of myocarditis in a pediatric population with clinical signs of severe cardiomyopathy. METHODS AND RESULTS: We retrospectively included 106 pediatric and adolescent cardiomyopathy (CMPY) patients requiring HTx, MCS, or any in-hospital treatment. DNA-sequencing was done and sequence variants were classified based on ACMG guidelines. Myocarditis was diagnosed according to the clinical protocol.We overall genotyped 106 index patients; 92 (87%) patients receiving HTx or MCS, 14 (13%) received in hospital treatment. 87 patients (82%) had dilated cardiomyopathy and 54 (51%) carried a (likely) pathogenic (P/LP) variant with TNNI3 as one of the leading affected genes. In 84 genotyped patients (80%) myocarditis was examined. 57 (68%) of the 84 had myocarditis, with chronic lymphocytic myocarditis in 34 (40%) cases. In 28 (49%) of 57 patients with and 14 (52%) of 27 patients without myocarditis P/LP-variants were found. In 41 cases (39%) genotyping of the parents suggests de novo P/LP-variants (34%). CONCLUSIONS: In severe CMPY, genetic causes and myocarditis because of infection are common. About 50% of childhood cardiomyopathies are linked to pathogenic genetic variants. Myocarditis signatures commonly observed in severe pediatric cardiomyopathies, are not necessarily specific and the only reason for early presentation of heart failure. Genotyping in severe CMPY is essential to identify the causes of myocarditis. Providing genetic counseling may support families facing challenging psychosocial situations.