A newborn with congenital mixed phenotype acute leukemia with complex translocation t(10;11)(p12;q23) with KMT2A/MLLT10 rearranged – a report of an extremely rare case

Neonatal congenital leukemia (CL) constitutes less than 1% of all childhood leukemia cases and is diagnosed in 1 to 5 per million live births. In the neonatal period acute myeloid leukemia (AML) is described in 56-64% of cases, acute lymphoblastic leukemia (ALL) in 21-38% of cases and mixed-phenotype acute leukemia (MPAL) in less than 5% of cases. Rearrangements of the mixed-lineage leukemia (KMT2A alias MLL) gene are found in > 70% of infant leukemia cases. The incidence of the most frequent KMT2A rearrangements in newborns with congenital MPAL is unknown. We report a male term newborn with “blueberry muffin” syndrome, which had been noted at birth, as a presenting sign of acute leukemia. Eight-color multiparameter flow cytometry showed a blast population corresponding to a myeloid lineage with monocytic differentiation positive for CD33+/CD15+/CD11c+/CD64+/HLA-DR+/CD4+, negative for MPO–/CD34–/CD19–/CD79a–/CD117–/CD13–/CD14–/CD36–/cCD3–/CD2–/CD7–, and additionally positive for sCD3 (40%). Mixed-phenotype acute leukemia according to the World Health Organization (WHO) classification was diagnosed with complex translocation t(10;11)(p12;q23) with KMT2A/MLLT10 rearrangement. The patient had an unfavorable response to chemotherapy and died on the 5th day of life.