Benign Acute Childhood Myositis (BACM) is a transient, self-limiting muscular condition that typically follows viral infections, especially influenza. The COVID-19 pandemic disrupted the circulation of respiratory viruses, altering the epidemiology of related post-infectious complications. This study investigates trends in BACM incidence, clinical features, and viral etiology before and after the pandemic. We conducted a retrospective study of BACM cases diagnosed at a tertiary children’s hospital in Italy between August 2017 and June 2025. Cases were grouped into pre-COVID (2017–2021) and post-COVID (2021–2025) periods. Demographic, clinical, laboratory, and virological data were analyzed. Incidence trends were compared with national ILI surveillance data. A total of 145 BACM cases were identified—28 pre-COVID and 117 post-COVID—corresponding to a 140% increase in incidence (IRR 2.41, 95% CI: 1.60–3.64, p < 0.001). Annual incidence rose progressively, closely mirroring the national trend in ILI circulation during the same period. Most cases occurred between December and February. Clinical presentation remained consistent, with a benign course and no major complications. Post-COVID cases showed significantly lower CK levels at discharge and shorter hospital stays (3 vs. 4 days, p = 0.011). Virological testing revealed a shift from influenza A (pre-COVID) to influenza B (post-COVID) as the predominant pathogen (p = 0.023).Conclusions: The post-pandemic rise in BACM incidence parallels the resurgence of ILI in Italy, likely reflecting changes in population immunity and viral dynamics. Despite this increase, BACM continues to present as a mild and self-limiting condition. Ongoing surveillance and clinical awareness remain essential during peak viral seasons.<Table Float="No" ID="Taba"> <tgroup cols="1"> <colspec align="left" colname="c1" colnum="1" /> <tbody> <row> <entry align="left" colname="c1"> What is Known: • Benign Acute Childhood Myositis (BACM) is a temporary, self-limiting condition in children following viral infections, historically linked to influenza A. </entry> </row> <row> <entry align="left" colname="c1"> What is New: • The incidence of BACM increased by 140% post-COVID-19, mirroring the rise in influenza-like illness. • There was a shift in viral cause from influenza A to influenza B, with later cases showing shorter hospital stays and lower creatine kinase levels. </entry> </row> </tbody> </tgroup> </Table>

Increase in benign acute childhood myositis in the post-COVID era: a retrospective study from a tertiary pediatric center

期刊论文
发表日期：

2025年9月5日

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Giacomo Brisca,
Marcello Mariani,
Tommaso Bellini,
Carla Cervello,
Margherita Di Jorgi,
Alessio Mesini,
Marina Francesca Strati,
Daniela Pirlo,
Claudio Bruno,
Emanuela Piccotti,
Elio Castagnola,
Andrea Moscatelli

摘要

Benign Acute Childhood Myositis (BACM) is a transient, self-limiting muscular condition that typically follows viral infections, especially influenza. The COVID-19 pandemic disrupted the circulation of respiratory viruses, altering the epidemiology of related post-infectious complications. This study investigates trends in BACM incidence, clinical features, and viral etiology before and after the pandemic. We conducted a retrospective study of BACM cases diagnosed at a tertiary children’s hospital in Italy between August 2017 and June 2025. Cases were grouped into pre-COVID (2017–2021) and post-COVID (2021–2025) periods. Demographic, clinical, laboratory, and virological data were analyzed. Incidence trends were compared with national ILI surveillance data. A total of 145 BACM cases were identified—28 pre-COVID and 117 post-COVID—corresponding to a 140% increase in incidence (IRR 2.41, 95% CI: 1.60–3.64, p < 0.001). Annual incidence rose progressively, closely mirroring the national trend in ILI circulation during the same period. Most cases occurred between December and February. Clinical presentation remained consistent, with a benign course and no major complications. Post-COVID cases showed significantly lower CK levels at discharge and shorter hospital stays (3 vs. 4 days, p = 0.011). Virological testing revealed a shift from influenza A (pre-COVID) to influenza B (post-COVID) as the predominant pathogen (p = 0.023).

Conclusions: The post-pandemic rise in BACM incidence parallels the resurgence of ILI in Italy, likely reflecting changes in population immunity and viral dynamics. Despite this increase, BACM continues to present as a mild and self-limiting condition. Ongoing surveillance and clinical awareness remain essential during peak viral seasons.

What is Known:

• Benign Acute Childhood Myositis (BACM) is a temporary, self-limiting condition in children following viral infections, historically linked to influenza A.

What is New:

• The incidence of BACM increased by 140% post-COVID-19, mirroring the rise in influenza-like illness.

• There was a shift in viral cause from influenza A to influenza B, with later cases showing shorter hospital stays and lower creatine kinase levels.