Three of the B-ALL-related NBN variants found in nine patients resulted in protein truncation, including the known loss-of-function variant p.K219fs (Figure 1B and Table 1).11 The remaining 22 variants were missense and preferentially located in the N-terminal FHA-BRCT-repeat domain (16 of 22 variants, 72.7%; Figure 1B). Here, NBN is linked to acute lymphoblastic leukemia.