MLL-PTD in a 13-year-old patient with blast phase myeloproliferative neoplasm: A case report.

RATIONALE: The risk of leukemic transformation in myeloproliferative neoplasm (MPN) has been increasing with time. Partial Tandem Duplications of the MLL gene (MLL-PTD) has been reported in de novo acute myeloid leukemia (AML), but not in MPN blast phase. The post-MPN AML developed adverse clinical outcomes, which showed no noticeable improvement over the past 15 years. Therefore, the mechanisms and therapeutic approaches of post-MPN AML need to be deeply studied.

PATIENT CONCERNS: In this study, we present a JAK2V617F positive MPN patient who experienced fatigue and splenomegaly, transforming into JAK2V617F negative AML.

DIAGNOSES: A diagnosis of acute monocytic leukemia was made in MPN blast phase.

INTERVENTIONS: The patient received chemotherapy and allogeneic hematopoietic stem cell transplantation (Allo-SCT).

OUTCOMES: The patient achieved complete remission twice, but relapsed twice. Relapse-free survival was only 3 months. She died about 24 months after her diagnosis.

LESSONS: MLL-PTD occurs in the progression of JAK2V617F positive MPN into JAK2V617F negative AML, which may be a novel mechanism of MPN blast phase and helpful for post-MPN AML diagnosis. Allo-SCT may be a good choice for post-MPN AML with MLL-PTD. More therapeutic strategies need to be explored for a better prognosis in these patients.