Benign Acute Childhood Myositis Before and After COVID-19: A Nine-Year Retrospective Study

Area of Science:

• Pediatrics
• Infectious Diseases
• Neurology

Background:

• Benign acute childhood myositis (BACM) is a common, self-limiting inflammatory myopathy affecting children.
• Understanding BACM's characteristics and seasonal patterns is crucial for diagnosis and management.
• The impact of the COVID-19 pandemic on BACM incidence requires investigation.

Purpose of the Study:

• To describe the demographic, clinical, and laboratory features of hospitalized children with BACM.
• To evaluate seasonal trends of BACM, including changes during the COVID-19 pandemic.
• To assess the association between viral pathogens, clinical presentation, and disease severity.

Main Methods:

• Retrospective single-center review of pediatric patients diagnosed with BACM (January 2016 - December 2024).
• Analysis of clinical, laboratory, and epidemiological data, including seasonal distribution.
• Identification of prodromal symptoms, presenting symptoms, creatine phosphokinase (CPK) levels, and associated pathogens.

Main Results:

• 47 BACM cases identified; male predominance (66%), median age 7 years.
• Most cases occurred in autumn/spring; common prodrome: fever, cough, rhinorrhea; presenting symptom: bilateral calf pain.
• Median CPK 4986 U/L (higher in boys, associated with longer stays). Influenza B most common pathogen (63%). No cases during 2020-2022 COVID-19 pandemic; increase in 2024.
• All patients recovered fully; median hospital stay 3.2 days.

Conclusions:

• BACM exhibits a distinct clinical and laboratory profile, characterized by self-limiting myopathy.
• The absence of BACM during the COVID-19 pandemic suggests a link to reduced viral circulation.
• Early recognition of BACM's typical presentation aids diagnosis and management, reducing unnecessary investigations.