UMEM Educational Pearls

Category: Pediatrics

Title: What is BACM?

Keywords: myositis, acute kidney injury, problems walking, calf pain (PubMed Search)

Posted: 2/14/2024 by Jenny Guyther, MD (Emailed: 2/16/2024) (Updated: 2/16/2024)
Click here to contact Jenny Guyther, MD

BACM stands for benign acute childhood myositis which is typically a benign, viral induced self limiting illness.  This was a retrospective study looking at 65 patients in Italy to further characterize the characteristics of the disease.

In this study, the median patient age was 6 years with a male predominance.  The incidence of BACM peaked in winter with a second peak in the fall.  Patients presented with prodromal symptoms including fever, cough, coryza, sore throat and vomiting.  The exam showed difficulty walking and myalgias with reproducible calf tenderness and preserved reflexes.  Influenza B and A, COVID and other viral pathogens have been detected in these patients.

Lab work may show an elevated creatinine kinase, AST and potassium.  WBC and CRP may also be elevated.  The median CK value was 943 U/L and on average normalized within one week.  Other studies have shown median CK values in the 3300s. Treatment includes hydration to promote CK clearance and prevent complications including acute kidney injury related to rhabdomyolysis.  Recurrent myositis or CK values > 5000 U/L should have screening tests for muscular dystrophy and metabolic disorders.


Attainaese et al.  Benign acute children myositis: 5 year experience in a tertiary pediatric hospital.  European Journal of Pediatrics, published online July 18 2023.