Ibrutinib, a first-in-class Bruton tyrosine kinase inhibitor has been approved by the Food and Drug Administration for the treatment of CLL in the United States.[7,8] This drug has shown beneficial effects including a higher overall response rate, sustained remissions, and a tolerable toxicity level.[9] Nevertheless, the adverse drug events of ibrutinib have seldom been systematically assessed. The gene discussed is BTK; the disease is B-cell chronic lymphocytic leukemia.