KMT2A and acute lymphoblastic leukemia: The four children with MLL-r positive relapse were on the GD-ALL 2008 protocol and the partner genotypes included one MLL-AF4, one MLL-PTD, and two MLL-ENL, all with solo BM relapse and high risk factors for poor prognosis such as WBC ≥50 × 109/L, T-cell phenotype, or D15 MRD positive (Table 5).