Benign acute childhood myositis: Factors associated with muscle symptoms and resolution.

Background: Benign acute childhood myositis (BACM) is associated with several viral infections. The aim of this study was to evaluate the progression of myositis symptoms, laboratory findings and oseltamivir treatment in children with influenza- and non-influenza-associated BACM. Methods: Patients aged 0–18 years old, admitted to the pediatric emergency department in the seasonal influenza period between 2018 and 2020 were retrospectively analyzed. Patients with acute onset calf tenderness, pain, difficulty in walking and elevated serum creatine phosphokinase were included and were grouped according to influenza rapid test kit results as influenza (A and B) positive, and influenza negative. The time to symptom resolution, laboratory data and the oseltamivir treatment were compared between the groups. Results: There were 94 patients (67 male, 27 female) with a mean age of 77 ± 22 months. Influenza A was detected in 21, influenza B in 27, and neither were detected in 46 patients. Time to symptom resolution of BACM was shorter in the influenza-positive patients than in influenza-negative patients (2.9 ± 1.4 days and 3.5 ± 1.5 days, respectively, P = 0.027). Oseltamivir did not reduce the symptom resolution time in influenza patients. All children had normal hemoglobin and platelet counts, elevated creatine phosphokinase and 76% of them had leukopenia. Neither clinical recurrence nor metabolic disease were reported. Conclusion: Symptoms of BACM tended to resolve slightly earlier in influenza-positive patients and the duration of symptoms was not affected by oseltamivir treatment. [ABSTRACT FROM AUTHOR]