Management and outcome of benign acute childhood myositis in pediatric emergency department

Background: Benign acute childhood myositis (BACM) is a self-limited syndrome associated with viral infections characterized by symmetric lower extremity pain typically affecting school-aged children. Evolution in rhabdomyolysis and kidney damage is rarely reported. Despite this, the acute presentation commonly concerns both parents and health care providers, often leading to unnecessary workup. The aim of the study was to determine the features and outcome of a large series of children with BACM identifying a management pathway for pediatricians in Emergency Department (ED). Methods: We conducted a retrospective study of patients with BACM managed in 2 Italian pediatric ED during a period of 8 and a half years. Demographic data, clinical, and laboratory results were extracted from electronic medical records. Recurrence, complications, treatments, and outcomes were also recorded. Descriptive statistics were produced for first-episode patients and for those with recurrence of myositis. A comparison between groups was performed. Results: One hundred and thirteen patients with BACM were identified. Ninety-two children (65 males) had a single episode, while ten (nine males) had recurrence. The mean age at presentation was 6.0 years (range 2–13,2). All patients had normal neurological examination and no one developed myoglobinuria, or renal failure. At first evaluation median CK level was 1413 UI/l (normal values < 150 U/L). Median CK of “recurrent” patients was higher than “non-recurrent” (2330 vs 1150 U/L, p = 0.009). Viral studies were positive in 51/74 cases, with high prevalence of Influenza viruses. Ninety-six patients (85%) were hospitalized with a median of 4 days. No patients had any residual muscular impairment. Conclusions: BACM has an excellent prognosis. Severe pathological conditions can be excluded with a complete history and clinical examination and simple blood and urine tests, avoiding unnecessary diagnostic investigations. Most patients may be discharged home from ED recommending hydration, rest, analgesics and careful follow-up.