[Clinical Analysis of 269 Ph Chromosome-Negative Myeloproliferative Neoplasms Patients Stratified by Age]

To investigate the difference of clinical characteristics between young patients(age≤40 years old) and middle-older patients(age>40 years old) with the myeloproliferative neoplasms（MPN）.

The clinical data (gene mutations， peripheral blood routine examinations， imaging examination and past history) of 269 MPN patients was collected and analyzed.

In essential thrombocythemia (ET) group, the proportion of triple-negative type in young patients was higher than that in middle-older group, while the peripheral white blood cell（WBC） and platelets（PLT） counts in the first visit were lower. In polycythemia vera (PV) group, the total detection rate of JAK2V617F (80.65%) was lower than that of other research reports. Young patients with PV showed the lower JAK2V617F rate and lower WBC count, compared with the middle-older aged patients. Both CALR and MPL mutations were not found in PV patients. There was only 1 primary myelofibrosis (PMF) patient aged <40 years old. 91.67% of the patients merged splenomegaly and this rate was higher than that of ET or PV patients. It was found that there were a diagnosed familial MPN family and an undiagnosed family， and the youngest patient was only 8 years old. The second-generation gene sequencing detection for them was not carried out.

Age is an important reference index in the assessment of risks. The MPN patients with different age and types show much difference in gene mutations, peripheral blood cell counts, thrombotic events and sizes of spleen. The onset ages of patients with familial MPN trends to be generational younger.