Transformation of an Unclassified Myeloproliferative Neoplasm with a RareBCR-JAK2Fusion Transcript Resulting from the Translocation (9;22)(p24;q11)

Abstract

BCR-ABL1negative myeloproliferative neoplasms (MPNs) are known to contain alterations of the tyrosine kinase JAK2 (located on 9p24) that result in constitutive activation of the encoded protein. JAK2 fusions are reported in acute and chronic leukemias of myeloid and lymphoid phenotypes. Here, we report an unclassified case of MPN (MPN-U) showing a t(9;22)(p24;q11), which generates aBCR-JAK2fusion gene by fusing theBCRat intron 13 toJAK2at intron 17 on the derivative chromosome 22. Most reported JAK2 fusions cases reveal an aggressive clinical course and long-term remissions have only been achieved after allogeneic stem cell transplantation (ASCT). To the best of our knowledge, this is the thirteenth case reported worldwide to describe aBCR-JAK2fusion transcript in MPN-U. The present report revealed a sustained complete clinical, hematologic, and cytogenetic remission 35 months after diagnosis and ~24 months after ASCT. RegardingBCR-ABL1  negativeMPN patients this case report provides strong support for a role ofJAK2activation in the oncogenesis and suggests a possible diagnostic and therapeutic target that should be investigated.