Coronavirus disease 2019 (COVID-19) generally presents with milder illness in children and adolescents than in adults; however, infants and those with underlying chronic conditions, obesity, or immunocompromised states remain at increased risk for severe dis-ease and death. Multisystem inflammatory syndrome in children (MIS-C) affects multiple organs, including the heart, gastrointestinaltract, and skin, and can result in severe illness requiring hospitalization or death. In children and adolescents, long COVID manifests with age-dependent, heterogeneous symptoms, leading not only to persistent physical complaints but also to neurologic manifestations and mental health problems. Therefore, evidence-based clinical guidelines and approved treatments for COVID-19 in children and adolescents remain limited, and research is needed to build a pediatric evidence base. Generating high-quality data is essential to develop optimized diagnostic and therapeutic strategies, establish standardized care pathways, and ultimately improve preparedness and outcomes for children and adolescents during future emerging infectious disease outbreaks. In this clinical information article, we review the epidemiology, clinical symptoms, complications, and drug treatment of COVID-19 in the pediatric population.

Objectives: This study used the Korean National Health and Nutrition Examination Survey (KNHANES) to determine the association between fractures and low muscle mass. Methods: This cross-sectional study used the 2010–2011 KNHANES data. Low muscle mass was defined as (appendicular skeletal muscle mass [kg]/Height2 [m2 ]) < 5.45 kg/m2 , which is < 2 SD below the sex-specific mean of a young reference group. Patients with T-scores between –1.0 and –2.5 indicated osteopenia, whereas those with T-scores lower than –2.5 indicated osteoporosis. Results: Out of 1,306 women enrolled in the study, 330 were diagnosed with low muscle mass according to the abovementioned diagnostic criterion. The prevalence of fractures at various sites was significantly higher in postmenopausal women with low muscle mass than in those without low muscle mass (relative risk [RR], 1.64; odds ratio [OR], 1.62; 95% confidence interval [CI], 1.06–2.48; P = 0.027). Furthermore, the prevalence of fractures was increased by the presence of osteopenia or osteoporosis in addition to low muscle mass (RR, 1.59; OR, 1.60; 95% CI, 1.02–2.49; P = 0.039) and by osteoporosis only (RR, 2.12; OR, 2.29; 95% CI, 1.11–4.70; P = 0.025). Conclusions Fracture was more prevalent in postmenopausal women with low muscle mass than in those without low muscle mass.This finding is consistent in a subgroup analysis that included women who had osteoporosis or osteopenia. Moreover, the risk of fractures increased as low muscle mass worsened.