Thrombosis History and Relationship with Low Thrombocytosis, Leukocytosis, and Jak2 V617F Mutation In A Cohort of 977 Patients with Essential Thrombocythemia (ET): Preliminary Report of the Registro Italiano Trombocitemia(RIT),

In essential thrombocythemia (ET) patients history of thrombosis and age over 60 y are validated risk factors for thrombosis; the thrombocytosis is a constitutive abnormality associated with both thrombotic and hemorrhagic risk; JAK2 V617F mutation, leukocytosis, and male gender are candidate thrombotic risk factors.

To evaluate in ET patients clinical-biological characteristics at diagnosis and their relationship with thrombosis occurrence before and after diagnosis.

A cohort of ET patients of the Registro Italiano Trombocitemia (RIT) was retrospectively analysed. This preliminary report in detail considers data on thrombosis history.

A total of 977 patients, 387 males and 590 females, presented at diagnosis: median age 55 y, median PLT count 783 × 109/L, median WBC count 8.8 × 109/L, median Hb 14.1 g/dL, bone marrow fibrosis (grade >0) in 33% of cases, history of thrombosis in 189 cases (19.3%). The patients at high risk (age over 60 y and/or history of thrombosis) were 511 (52 %). The thrombosis history in univariate analysis was significantly related to: age over 60 y (p 0.001), male gender (p 0.045), low thrombocytosis (PLT <783 x109/L, p 0.001), leukocytosis (WBC >8.8 x109/L, p 0.01), and JAK2 V617F mutation (p 0.006). No relationship was found with the bone marrow fibrosis.

The 977 patients, when both PLT count and WBC count at diagnosis were considered, were subdivided in four groups: group 1: 202 pts with low thrombocytosis and leukocytosis; group 2: 270 pts with low thrombocytosis and no leukocytosis; group 3: 272 pts with high thrombocytosis and leukocytosis; group 4: 197 pts with high thrombocytosis and no leukocytosis. In those patients, the thrombosis history was: 26.7% in the group 1(both risk factors); 24.1% in the group 2 (PLT risk factor); 20.2% in the group 3 (WBC risk factor); 7.6% in the group 4 (no risk factors). The rate of thrombosis history in patients with one or two of these risk factors was significantly (p 0.001) higher than in patients with no risk factors. The thrombotic events during the follow up (4088 pt-y) are still object of analysis.

In this cohort of ET patients the rate of thrombosis history in univariate analysis was related to age over 60 y. Moreover, a significant relationship was found with PLT count at diagnosis below the median value (783 x109/L), WBC count at diagnosis over the median value (8.8 x109/L), JAK2 V617F mutation, and male gender.

No relevant conflicts of interest to declare.