BTK is a key component of the B-cell antigen receptor (BCR) signalling pathway.16,18 Disruption in B-cell activities can result in autoimmune diseases such as arthritis, and mutations in B-cells and their precursors can cause a range of cancers, such as leukaemia and lymphoma.183 was originally approved for chronic lymphocytic leukaemia (CLL), and later for mantle cell lymphoma (MCL) and Waldenström macroglobulinemia, with approvals for other lymphomas following. The gene discussed is BTK; the disease is mantle cell lymphoma.