The comparison of the accompanying Exonseq data of samples positive or negative for CYB5Aalt did not show any differences in regional coverage suggesting that no genomic deletion detectable by exon coverage can explain de novo transcription of CYB5Aalt. Rather, the HeH subtype has been described to be widely hypomethylated (23) and first Hi-C experiments suggest a wide dysregulation of 3D-chromatin architecture in this subtype compared to ETV6-RUNX1 BCP-ALL [54], making epigenetic dysregulation a probable cause for this genetic event. The gene discussed is RUNX1; the disease is acute lymphoblastic leukemia.