ATM and B-cell chronic lymphocytic leukemia: In addition to TP53 and ATM genetic defects, chemoresistance might be a consequence of other defects in the DDR, especially because more than 50% of chemo-refractory CLL patients do not exhibit TP53 or ATM aberrations.5 Therefore, the RT-MLPA could be a very useful tool to detect ATM-p53 dysfunctional patients in the absence of ATM and/or TP53 mutations.