Clinical Characteristics of JAK2 V617F Mutation Positive Acute Myeloid Leukemia.

Chronic myeloproliferative diseases (CMPD) are clonal disorders of pluripotent hematopoietic stem cells. Acquired JAK2 V617F point mutation has recently been identified as disease causing activating genetic abnormality in classic BCR-ABL negative CMPD (80% of polycythemia vera, 35% of essential thrombocythemia and 50% of chronic idiopathic myelofibrosis cases). JAK2 V617F is rare in other myeloid stem cell disorders like acute myeloid leukemia, chronic myelomonocyter leukemia or myelodysplasia with reported frequency of 3–8%. Between January 2001 and December 2005 155 consecutive adult patients [87 females and 68 males, median age of onset was 49±14 (range 18–83) years] were diagnosed with AML in our institute. Peripheral blood or bone marrow samples drawn at the time point of diagnosis were analyzed for the presence of JAK2 V617F by allele-specific PCR. JAK2 V617F mutation was present in 5 patients (3 males and 2 females; 3.2%). 3 of the 5 patients had prior history of CMPD, while 2 patients were diagnosed with de novo AML. The clinical characteristics and laboratory features of JAK2 V617F positive patients are shown in Table 1. FLT3 internal tandem duplication, FLT3 tyrosine kinase domain mutations, AML1-ETO, CBFB-MYH, PML-RARA rearrangements or nucleophosmin mutations were not present at the time point of AML diagnosis. In the case of patient 1, thrombocytosis was present prior the diagnosis of AML, and bone marrow biopsy revealed grade 3 fibrosis at diagnosis of AML, suggesting the presence of an atypical CMPD with the coexistence of del(5q) MDS. Patient 2 had no remarkable disease in his previous medical history. Induction therapy resulted in complete hematological and cytogenetic remission with persistent JAK2 V617F positivity. 10 month later clinical features of CMPD (elevated white blood cell count, left shifted peripheral blood smear, hepatosplenomegaly) appeared. In conclusion, these two cases suggest that acute myeloid leukemia with JAK-2 V617F mutation in fact corresponds to the blastic transformation of a clinically atipical chronic myeloproliferative disorders.