First Philippine report of myeloproliferative neoplasms with concurrent JAK2 and BCR::ABL1 mutations

Myeloproliferative neoplasms (MPNs) are broadly classified into BCR::ABL1 -positive chronic myeloid leukaemia (CML) and BCR::ABL1 -negative subtypes such as polycythaemia vera (PV), essential thrombocythaemia and primary myelofibrosis. Although traditionally considered mutually exclusive, rare cases of coexisting BCR::ABL1 rearrangement and Janus kinase 2 ( JAK2 ) mutation have increasingly been recognised.

We report the first Philippine case series of three patients with concurrent CML and JAK2 -positive MPNs. Two patients developed PV 6–9 years after the initial diagnosis of CML despite ongoing tyrosine kinase inhibitor (TKI) therapy and molecular response, while a third patient had persistent thrombocytosis and was later found to have a concomitant JAK2 -mutated MPN with fibrotic marrow features after 4 years.

Compared with previously reported cases, our series demonstrates similarly delayed emergence of JAK2 -mutated clones while highlighting real-world challenges in TKI intolerance, sequential TKI use and the need for combined cytoreductive strategies in a resource-limited setting.