IFNA2 and congenital rubella syndrome: Notably, several key metabolites involved in arginine metabolism (e.g., arginine, glutamine, and aspartic acid, citrulline, urea, and proline) displayed strong correlation with CRS-related cytokines (e.g., IL-6, IL-1β, M-CSF, IL-12 p70, IFN-α2) in severe patients (Fig. 2f).