Relationships between JAK2 mutation and clinical characteristics of patients with Philadelphia-negative myeloproliferative neoplasm

Introduction: Philadelphia-negative chronic myeloproliferative neoplasms (Ph-negative MPN) which include polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) are known to have a propensity to develop thrombosis, bleeding, myelofibrosis and acute leukemia. Objective of this study was to evaluate the prevalence and significance of JAK2 mutation in Ph-negative MPN patients and evaluate the prognostic factors leading to morbidity and mortality. Method: This study included retrospective reviews of Ph-negative patients diagnosed and treated in the Hematology Divisions of Rajvithee and Thammasat Hospitals, Thailand from 1 January 2002 to 31 December 2011. JAK2 mutation was established by allele-specific polymerase chain reaction (PCR). Result: There were 73 Ph-negative MPN patients including 28 with ET, 44 with PV, and 1 with PMF. The incidence of JAK2 mutation was 54.8% (40/73 cases), 61% in PV patients (27/44 cases) and 46.4% in ET patients (13/28 cases). The significant factor associated with positive JAK2 mutation was age over 59 years (OR 2.06, 95%CI=1.59 - 11.45, p = 0.003). Other factors had no statistical significance. A white blood cell count (WBC) of over 12,000/mm3 and a platelet count of over 400,000/mm3 presented as major risks for bleeding complications in PV patients. (OR 1.36, 95%CI=1.09 - 1.69, p = 0.008 and OR 1.38, 95%CI=1.10 - 1.73, p = 0.006, respectively). Discussion a nd Conclusion: This study showed having an age of atleast 59 years was associated with a high rate of JAK2 mutation. Elevated WBC counts and platelet counts correlated well with increased bleeding in PV patients.