PLCG2 and B-cell chronic lymphocytic leukemia: Thus, we hypothesize that the Δ19 and Δ20-22 deletions of the PLAID mutants, unlike the S707Y point mutation of APLAID and CLL ibrutinib resistance, cause a loss of the rigid orientation of the catalytic dyad normally brought about by the SH2n-SH2c-SH3 tandem.