The global loss of H3K27me3 in patients with these mutations corresponded with our finding of lower levels of H3K27me3 in patients with AHD; 54% of the AML patients with ASXL1, BCOR, U2AF1 and/or SRSF2 were diagnosed with AHD compared to only 18% of the patients without these (p < 0.01). The gene discussed is BCOR; the disease is mitochondrial DNA depletion syndrome 4a.