Hospitalized Versus Outpatient Benign Acute Childhood Myositis: A 10-Year Single-Center Experience.

Background and Objectives: The objectives of this study were to compare the clinical, laboratory, and etiological characteristics, as well as outcomes, of hospitalized and outpatient children with benign acute childhood myositis (BACM) and to identify factors associated with hospitalization. Materials and Methods: This retrospective single-center study included children diagnosed with BACM over a 10-year period. Demographic data, clinical features, laboratory parameters, etiological agents, treatments, hospitalization status, and recurrence were analyzed. Hospitalized and outpatient patients were compared to determine factors associated with hospital admission. Results: A total of 93 patients were included. Hospitalized patients had significantly higher creatine kinase (CK) levels and a higher frequency of inability to walk compared with outpatients. No significant differences were observed between the groups regarding age, sex, gastrointestinal symptoms, serum creatinine levels, or inflammatory markers. Influenza A (INFA)-associated BACM was characterized by lower CK levels and shorter fever duration, whereas viral panel negative (VPN) cases had longer symptom duration and were more frequently hospitalized. Notably, sandfly fever virus was identified in two hospitalized patients, representing an uncommon but clinically relevant etiological agent in our cohort. Rhabdomyolysis occurred in three patients, all of whom were hospitalized and recovered without sequelae. The recurrence rate was 11.8%, with no significant association between recurrence and demographic or clinical variables. Conclusions: Although BACM is typically self-limiting, elevated CK levels and inability to walk may help identify patients who require hospitalization. Etiological differences influenced disease severity, and the detection of sandfly fever-associated BACM highlights the importance of considering regional viral agents in the differential diagnosis.