Benign Acute Children Myositis: Five Years’ Experience in a Tertiary Care Pediatric Hospital

Abstract

Purpose: Benign acute childhood myositis (BACM) is a self-limited childhood illness, and it is mainly caused by viral infections. Clinical and laboratory alterations usually normalize rapidly; generally, the only medical intervention required is supportive (hydration, analgesic medication). The low awareness about BACM often led to delayed diagnosis and unneeded ancillary investigations. This study aims to better characterize the clinical and laboratory features of BACM to improve the diagnostic process and inpatient and outpatient management. Materials and methods: We conducted a retrospective study selecting all children admitted to Meyer's Children's Hospital-IRCCS (Florence, Italy) with a diagnosis of BACM over the last 5 years. Clinical, laboratory, and instrumental data were collected from electronic clinical records and analyzed. Results: Sixteen patients were enrolled. The median age was 7.68 years (IQR 5.7-12.9). Male gender (62.5%) and Caucasian ethnicity (68.75%) were prevalent. Most of the patients were admitted during winter, and a second peak has been found in summer. All patients had bilateral calf pain at admission (87.5%), associated with asthenia, and refuse to walk (93.7%). Prodromal symptoms were fever (81.25%), cough (37.5%), coryza (43.5%), sore throat (50%), and vomiting (31.25%). The median value of CPK was 2,183.5 U/L (IQR 1,395.5-7,156.25) at peak. CPK median time to normalization was 7 days (IQR 7-8.5) from the nadir. Influenza B was the virus most frequently BACM associated, followed by influenza A; a novel association with Sars-CoV-2 has been detected. Two patients had pathogenic variants at the Next Generation Sequencing myopathies panel. Conclusions: School-aged children admitted to the hospital with walking difficulty and myalgia generally after an upper respiratory tract infection with a moderate CPK elevation should remind at first of BACM. Rapid complaint resolution and biochemical markers normalization will prevent unnecessary tests and inappropriate therapies.