Benign acute children myositis: 5 years experience in a tertiary care pediatric hospital.

Benign acute childhood myositis (BACM) is a self-limited childhood illness, and viral infections mainly cause it. Clinical and laboratory alterations usually normalize rapidly; generally, the only medical intervention required is supportive (hydration and 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. 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, both those visited at Emergency Department (ED) and those admitted to the Pediatric Unit. Clinical, laboratory, and instrumental data were collected from electronic clinical records and analyzed. Overall, sixty-five patients were enrolled; 49 children were visited and discharged directly from ED, whereas 16 were admitted in the Pediatric or Neurologic Wards. The median age was 6.56 years (IQR 4.9-9.1). Male gender (66.1%) and Caucasian ethnicity (70%) were prevalent. Most patients were admitted during winter, and a second peak was found in autumn. All patients had bilateral calf pain, most of them (87.7%) associated with asthenia and refuse to walk (93.8%). Prodromal symptoms were fever (75.3%), cough (32.3%), coryza (26.1%), sore throat (26.1%), and vomiting (15.3%). The median value of CPK was 1827 U/L (IQR 915.5-2462) 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.    Conclusion: 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. What is Known: • BACM is a self-limited syndrome associated with acute infections. Influenza A and B viruses are the main etiological agents, but BACM may be related to many other microorganisms like Parainfluenza virus, Epstein-Barr virus, Cytomegalovirus, Human herpesvirus 6, Respiratory syncytial virus, Coxsackieviruses, Mycoplasma pneumoniae, Streptococcus pyogenes, Legionella, and Salmonella spp. • Clinical and laboratory alterations usually normalize rapidly; generally, the only medical intervention required is supportive (hydration, analgesic medication). Evolution in rhabdomyolysis and kidney damage is possible but rarely reported. What is New: • Sars-CoV-2 could be an emerging possible cause of BACM. During and after the Sars-CoV-2 outbreak, virus infection seasonality has changed, and so has BACM seasonality. • Screening tests for muscular and metabolic disorders are recommended in recurrent myositis and/or cases with marked CPK elevation (≥ 5000 U/L).

From influenza to SARS-CoV-2: etiological evaluation of acute benign childhood myositis.

AIM: To present the etiological evaluation results of our acute benign childhood myositis cases. MATERIALS AND METHODS: Children, who were referred to pediatric neurology outpatient clinic in Maternity and Children's Hospital, with difficulty in walking and high creatinine kinase levels were evaluated. Viral and bacterial serological evaluation of children were performed by real-time polymerase chain reaction method. RESULTS: Twenty-five children (21 M,4 F) included in the study. The most common complaints were walking difficulty and tenderness, pain on the gastrocnemius muscles. Their creatine kinase levels were between 216 and 8770 IU. Twenty-two children were hospitalized. Analgesic, intravenous fluid, antibiotic and/or antiviral drugs were given. The most common etiologies were influenza A and B. One children was diagnosed as suspected COVID-19 by the symptoms and the findings in thorax computerized tomography but the SARS-CoV-2 PCR and antibody tests were negative. CONCLUSION: School-aged children admitted to hospital with walking difficulty generally after an upper respiratory tract infection with a moderate creatine kinase elevation should remind at first acute benign myositis. Resolution of the complaints in a short time and normalisation of the biochemical markers will prevent unnecessary tests. Endemic and pandemic infections may cause this entity as well.