Abstract: Objective To investigate JAK2, CALR and MPL gene mutations in patients with classical BCR-ABL1-negative myeloproliferative neoplasms (MPNs) and to analysis their clinical features. Methods This retrospective study analyzed clinical and laboratory data from 126 patients with classical BCR-ABL1-negative MPNs diagnosed from July 2017 to July 2019 for two consecutive years at a single center. Results ①JAK2 V617F mutation is the highest frequency in MPNs patients, accounting for 77.78%, and in PV patients, accounting for 95.24%. Among the ET patients,JAK2 V617F mutation-positive patients had significantly higher hemoglobin levels than triple-negative patients, and were older than CALR mutation-positive patients（P<0.05）; Among the PMF patients, JAK2 V617F mutation-positive patients had significantly higher white blood cell counts than triple-negative patients （P<0.05）. ②The incidence of thrombotic events in patients aged ≥60 years was significantly higher than that in patients aged <60 years（P=0.015）. WBC, PLT and fibrinogen（Fb）in the thrombus group were significantly higher than those in the non-thrombosis group（P<0.05）. Conclusion Patients with classic BCR-ABL1-negative MPNs have a high level of JAK2 V617F mutation. JAK2 V617F positive patients, old age（≥60 years）, patients with high WBC counts, high PLT counts and high Fb levels are associated with higher risk of thrombotic events.

Key words: Myeloproliferative neoplasms, BCR-ABL1 negative, Janus kinase2, Myeloproliferative leukemia virus oncogene, Calreticulin