Concurrent RUNX1::MECOM and RUNX1::PRDM16 Fusions from a Novel Genomic Breakpoint: First Report of a Dual-Fusion Mechanism in Acute Myeloid Leukemia.

While complex fusions involving three chromosomes are already uncommon in AML, the formation of two distinct fusion genes from an identical breakpoint is exceptionally rare. This paper reports the adult case of acute myeloid leukemia harboring dual fusion genes RUNX1::MECOM and RUNX1::PRDM16, both originating from the same RUNX1 breakpoint (chr21:36206707, hg19). The 62-year-old male patient presented with primary refractory acute myeloid leukemia (AML), failed to achieve remission after induction chemotherapy, and had an overall survival of only 3 months. The RUNX1::PRDM16 translocation was cryptic and resulted in PRDM16 overexpression, which is associated with poor prognosis. Integrated molecular profiling revealed concurrent mutations in FLT3-ITD, U2AF1, and PTPN11, collectively indicating a very high disease risk. This case provides the first evidence for the novel mechanism of dual fusion gene formation from a single genomic breakpoint.