Respiratory syncytial virus (RSV) bronchiolitis is the leading cause of hospitalization in infants without any effective treatment strategies. Identification of biomarkers associated with disease severity may be significant in improving management. However, several studies have failed to identify specific biomarkers for bronchiolitis. Serum secretory acid sphingomyelinase (S-ASM) activity has been considered a biomarker of cytokine release, inflammation, and oxidative stress in various diseases. This study aimed to evaluate whether serum S-ASM activity increases and correlates with disease severity in infants with RSV bronchiolitis. Serum S-ASM activity was measured in 31 infants with RSV bronchiolitis, 9 infants with RSV-negative febrile infection, and 8 healthy infants. Laboratory data and clinical observational findings were analyzed for correlation with serum S-ASM activity. Serum S-ASM activity was significantly higher in the 31 infants with RSV bronchiolitis (9.5±5.4 nmol/mL/h) than individuals in the control groups (RSV-negative febrile infection patients : 4.3±1.9 mol/mL/h, p<0.005 ; healthy infants : 4.0±1.4 nmol/mL/h, p<0.005). Serum S-ASM activity was negatively correlated with interferon-γ levels (rho=−0.448, p=0.012) but not with any other outcomes. Serum S-ASM activity was significantly higher in infants with RSV bronchiolitis than in individuals in the control groups ; however, its clinical significance requires further investigation
