In a recent study, characteristics and outcomes with myeloproliferative neoplasms (MPNs) in patients younger than 39 years were examined, and a relatively high incidence of thromboembolic events was found in patients in this age group. The study results were reported in the Annals of Hematology.1

Classical forms of MPNs occur with a median age at diagnosis of 60 to 72 years, and these conditions are rare in younger patients, while incidence increases with age, the study’s researchers explained in their report. They also noted that there are possible differences in characteristics associated with MPNs in pediatric patients versus patients with an advanced age.

The researchers obtained data on patients younger than 39 years of age with newly diagnosed MPNs from the National Health Insurance Service in the Republic of Korea. Several outcomes were explored using these data, including evidence of disease transformation (to secondary myelofibrosis or secondary acute myeloid leukemia), thromboembolic events, and secondary primary malignancies.

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A total of 990 patients were included in the analysis, which had a median follow-up of 57.5 months (range, 6-131). In these patients, essential thrombocythemia (ET) occurred in 643 patients (64.9%), with an incidence of 2.53 persons per 1,000,000. Polycythemia vera (PV) occurred in 347 patients (35.1%), with an incidence of 1.37 per 1,000,000.

Thromboembolic events were reported in 16.7% of patients overall, at a median 7.1 months (range, 0-121.4) following MPN diagnosis. Thromboembolic events occurred in patients with ET at a 5-year cumulative incidence of 14.2% and in patients with PV at a 5-year cumulative incidence of 21.3% (P =.0008). Aspirin and hydroxyurea treatment appeared to be linked to a lower incidence of arterial thromboembolic events.

Secondary primary malignancies were reported in 3.2% of patients overall, with a median time of 36.8 months (range, 4.2-124.5) following ET or PV diagnosis. They occurred at 5-year cumulative incidences of 2.5% in patients with ET and 2.6% with PV (P =.570). Hydroxyurea was associated with a higher incidence of secondary primary malignancies.

The researchers considered the rates of ET and PV to be low in this population, with ET being the more common of these 2 types of MPNs. They also indicated the incidence of thromboembolic events in this analysis should warrant thrombosis prevention, and that hydroxyurea use seems linked to higher secondary primary malignancy incidence.


  1. Choi HS, Hong J, Hwang SM, et al. Evaluation of the need for cytoreduction and its potential carcinogenicity in children and young adults with myeloproliferative neoplasms. Ann Hematol. Published online July 30, 2021. doi:10.1007/s00277-021-04527-7