Shedding New Light on the Magnitude of Thrombosis Risk in Patients With Myeloproliferative Neoplasms

ARTICLE: Shedding New Light on the Magnitude of Thrombosis Risk in Patients With Myeloproliferative Neoplasms

AUTHORS: Alison R. Moliterno and Elizabeth V. Ratchford

JOURNAL: Ann Intern Med. 2018 Jan 16. doi: 10.7326/M17-3153. [Epub ahead of print]

Myeloproliferative diseases were first described by William Dameshek in 1951. In 2008, the World Health Organization established a new classification system and introduced the term “myeloproliferative neoplasms” (MPNs). Polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) are the most prevalent MPNs and are characterized by overproduction of leukocytes, erythrocytes, or platelets; development of bone marrow fibrosis; leukemic transformation; and arterial and venous thrombosis. When Dameshek proposed the term “myeloproliferative diseases,” he also proposed the presence of a then-undiscovered stimulus that drove proliferation. We now understand that mutation of the JAK2 gene, JAK2 V617F, is the most common stimulus, occurring in 95% of patients with PV and 60% of those with ET or PMF. Myeloproliferative neoplasms are relatively rare; are acquired in middle to older age; and are, despite their classification as neoplasms, indolent diseases, with survival measured in decades (1). Yet, MPNs exhibit marked variability in disease presentation and outcomes, especially with regard to thrombotic events.

In this issue, Hultcrantz and colleagues report a study that examined thrombosis patterns in 9429 Swedish patients with MPNs diagnosed between 1987 and 2009 compared with 35 820 matched control participants (2). As in prior studies, both arterial and venous thrombotic events were increased in patients with MPNs, with the highest risk around the time of MPN diagnosis, although risk persisted throughout patients' lifetimes. Older age and male sex increased cumulative risk for both arterial and venous events in patients with MPNs compared with the general population, but thrombotic risk was higher in the MPN group regardless of age or sex. Of note, the highest hazard ratio that Hultcrantz and colleagues observed was for venous events in the youngest age group.

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