Acute myositis in the paediatric emergency department

Introduction: benign acute childhood myositis (BACM) is a benign, self-limiting disease currently believed to be a sequela of viral infections. The typical clinical presentation is myalgia in the lower extremities accompanied by refusal to walk.

Patients and methods: we did a retrospective review of all the cases of BACM managed in our paediatric emergency department over a 25-year period. We collected data on demographic, clinical and laboratory variables through the systematic review of health records. We performed a descriptive statistical analysis, followed by comparison of groups with the Mann-Whitney U test. The correlation between quantitative variables was assessed by means of the Spearman rank coefficient.

Results: we identified 139 cases of BACM (74.8% in male patients). The highest incidence corresponded to children aged 4 to 8 years and the winter months. Bilateral lower limb myalgia was the most frequent presenting complaint. Fever was reported in 86.3% of cases, accompanied by respiratory symptoms (88.5%); influenza virus infection was confirmed in 37 cases (75.6% serotype B). At diagnosis, the median creatine kinase (CK) level was 1794 U/l, with no significant differences between the sexes (p=0.687). All patients had normal renal function, and none required hospitalization.

Conclusions: based on its clinical and analytical manifestations, BACM is easy to recognise. Although massive elevation of CK is common, complications are rare, and most patients can be discharged with conservative treatment.