Benign acute childhood myositis: A 5-year retrospective study

Benign acute childhood myositis (BACM) is a rare, transient, and self-limited inflammatory condition of the skeletal muscle that usually occurs after a viral infection. It affects pre-school and school-aged children at a median age of 6-9 years, with a male predominance. Patients can be managed with analgesia, rest, and adequate hydration at home.

A retrospective review was carried out of patients' clinical records with an elevated level of creatine phosphokinase (CPK) who presented to the pediatric emergency department between January 1, 2015 and December 31, 2019.

Out of 174 cases of elevated CPK values, 100 corresponded to BACM-compatible clinical presentations (n = 96). There was a male predominance (77%) with a median age of 6 years. There were more cases registered in 2019 compared with the previous years. The most frequently reported prodromal symptoms were fever, cough, and rhinorrhea. Bilateral calf pain was the most frequently reported BACM symptom, followed by gait complaints and refusal to walk. Hospitalization was an independent predictor of CPK levels. In two cases there was myoglobinuria. The most common hematological findings were leukopenia and thrombocytopenia.

Our results regarding male predominance, median age, and hematological findings are similar to the published reports. The outbreak during 2019 coincided with the 2019/2020 flu season. During this period, influenza B was the most prevalent virus and it is known to be the most myotrophic one. Physicians often take into consideration CPK levels during inpatient admission. All patients recovered fully, emphasizing the fact that BACM is benign, self-limited, and with an excellent prognosis.