The concurrent ibrutinib cohort exhibited low CRS severity compared to No-ibrutinib cohort (Grade ≥ 3 CRS: ibrutinib, 0%; No-ibrutinib, 26%; p = 0.05) and peak serum concentrations of CRS-related cytokines (IL-8, IL-15, MCP-1). Here, CXCL8 is linked to congenital rubella syndrome.