PLCG2 and B-cell chronic lymphocytic leukemia: In comparison with the previously estimated growth rate of CLL cells in a heterogeneous group of patients ranging from −0.29 to 0.71% per day12, the dominant clone at the start of ibrutinib therapy (clone 4, Fig. 1d) was estimated to decline at a rate of 0.2% (±0.2%) per day, while its progeny clones containing the PLCG2 mutation grew at a rate of 1.5–1.9%±0.1–0.2% per day.