Here, we describe NUP98::ASH1L as a previously unrecognized NUP98 gene fusion and discuss its possible pathogenetic contribution to early relapse after allogeneic hematopoietic stem cell transplantation (alloHSCT) in a patient with secondary AML and prior myelodysplastic/myeloproliferative neoplasia with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T). The gene discussed is NUP98; the disease is myelodysplastic syndrome.