We identified significant transcriptomic correlations with infection at 3 months following ibrutinib treatment, with patients who developed subsequent infection demonstrating upregulation of inflammatory pathways, such as IL‐6/ JAK/ STAT3 signalling, interferon gamma and alpha signalling, IL‐2/ STAT5 signalling, complement, apoptosis, TNFa signalling and reactive oxygen species. The gene discussed is STAT3; the disease is infection.