Clinical Spectrum of Children With Parvovirus B19–Associated Acute Myocarditis

BACKGROUND: Parvovirus B19 is a DNA virus transmitted via respiratory droplets, commonly causing erythema infectiosum in children but also implicated in acute myocarditis. In 2024, an outbreak of parvovirus B19 infections was reported across Europe and the United States. Despite growing awareness, data on the clinical features and outcomes of children with parvovirus B19–associated acute myocarditis remain limited. METHODS: This multicenter retrospective observational study reviewed medical records of pediatric patients (<18 years of age) admitted with acute myocarditis to 11 Italian tertiary pediatric cardiac centers between January 1, 2022, and October 31, 2024. Of 217 cases, 66 had confirmed parvovirus B19 DNA in plasma (PVB19 + ), whereas 82 with negative parvovirus B19 testing served as a comparator group (PVB19 − ). Population-based incidence trends of pediatric myocarditis were also evaluated in the Lombardy region from 2004 through 2024. RESULTS: Among PVB19 + acute myocarditis cases, 58 of 66 (87.9%) were admitted in 2024. The median age was 32 months, with 51 of 66 (77.2%) ≤7 years of age, and 36 of 66 (54.5%) were boys. Median plasma viral load was 34 411 copies/mL, whereas only 30 of 56 (53.6%) had immunoglobulin M (IgM) positivity. Among 26 of 66 (39.4%) with available histology, 23 (88.4%) had lymphocytic myocarditis, and parvovirus B19 DNA was identified in 84.0% of myocardial specimens. Among 25 of 65 (38.4%) who underwent genetic testing, none had pathogenic or likely pathogenic variants. Overall, 13 of 66 (19.7%) died, underwent heart transplantation, or received a durable left ventricular assist device (in total, there were 6 deaths, 5 durable left ventricular assist devices, and 5 transplantations) compared with 1 of 82 (1.2%) among PVB19 − acute myocarditis (one patient who received a durable left ventricular assist device and later underwent transplantation; P <0.001). A marked increase in regional and institutional myocarditis incidence in pediatric acute myocarditis was observed in 2024, predominantly in children ≤7 years of age, driven by PVB19 + cases. CONCLUSIONS: During the 2024 parvovirus B19 outbreak, pediatric PVB19 + acute myocarditis cases surged in Italy and were associated with severe outcomes. A high index of suspicion is required for diagnosis, and early virological testing is essential to guide management and potentially improve outcomes.