A subset of B‐cell acute lymphoblastic leukaemia (B‐ALL) cases is associated with D4Z4 insertions in the IGH (and rarely ERG) locus in both orientations and with various reading frames, leading to expression of truncated DUX4 variants or hybrid DUX4‐IGH fusion proteins containing the DUX4 homeodomains (Lilljebjorn et al, 2016; Yasuda et al, 2016). The gene discussed is DUX4; the disease is precursor B-cell acute lymphoblastic leukemia.