PLCG2 and B-cell chronic lymphocytic leukemia: Mutations in PLCγ2 and/or Btk have been reported in 11 to 90% cases of Ibrutinib-refractory CLL, further underscoring the importance of better understanding the process by which the partnership of Btk and PLCγ2 drives CLL disease progression (122, 123, 124, 125, 126).