OBJECTIVETo investigate JAK2V617F mutation and its clinical significance in patients with chronic myeloproliferative disorders (cMPD).

METHODSA retrospective study was performed on 523 cMPD patients diagnosed according to the current World Health Organization (WHO) criteria. Allele-specific PCR (ASP) was used to identify JAK2V617F mutation, the mutation status was analyzed by PCR-RFLP, and the results were confirmed by sequence analysis. The mutation burden was calculated by the ratio of T/G. The correlation between the allele burden and the clinical and hematologic features was analysed. For those without JAK2 V617F, MPL W515L mutation was analyzed.

RESULTSJAK2 V617F was detected in 66% of all patients (94% in PV, 80% in ET, 78% in CIMF, 75% in CMPD-U and 14% in HES). The majority of patients carried JAK2 V617F mutation were heterozygous , homozygote was found in only 5 cases (4 in PV and 1 in ET). The mutation burden in most patients (71.5%) was low with PV>ET>CIMF (P =0.003). Hemoglobin level was significantly related to high mutation burden in PV (r = 0. 203, P =0.033). Bone marrow megakaryocyte counts were found to be marked increased in ET with high JAK2 V617F loads (P = 0.024), and hepatomegaly in CIMF was significantly associated with high JAK2 V617F mutation burden (r = 0.315, P = 0.001).

CONCLUSIONS1) Most cMPD patients, especially those with PV, carry JAK2 V617F mutation, except for CML. 2) .98% of JAK2 V617F mutation occurs of heterozygous status. 3) The mutation burden is PV>FT>CIMF. High JAK2 V617F loads are significantly associated with higher hemoglobin level in PV and higher bone marrow megakaryocyte counts in ET. 4) The positive correlation between hepatomegaly and JAK2 V617F mutation burden is found in CIMF.