PB2045: POLYCYTHEMIA VERA IN YOUNG SUBJECTS: ABOUT A COHORT OF 11 CASES

Abstract

Background: Polycythemia Vera (PV) is a typical Philadelphia-negative (Ph_) myeloproliferative disease. It is secondary in 95% of cases to the JAK 2 mutation on exon 14. The median age at diagnosis is 65 years. PV is unusual in young patients, so that little information is available on long-term clinical evolution in this particular group. Aims: The aim of this study is to describe the clinical presentation, biologic features, treatment approaches, and long-term outcome especially the risk of thrombosis. Methods: Of all the 64 patients followed in our department for PV, we report 11 cases aged less than 55 years. The inclusion criteria were a diagnosis satisfying the PVSG criteria and, from 2016 on, the WHO criteria. Secondary causes of erythrocytosis were carefully ruled out in all patients. At diagnosis, cytogenetic and molecular analysis were not done in our patients. Search for JAK2 mutation and serum EPO dosage were performed in all cases. Results: PV in young patients represents 17% of all PV followed. Median age of our population is 44 years, range 32-52, with 27% of patients under 40 years old. slightly more often in men with (sex ratio 1.75). Arterial hypertension is the most common comorbidity and it is a cardiovascular risk factor in the majority of patients. A thromboembolic event revealing PV is found in 2 patients. The main clinical signs were significant burning sensation in fingers and palms due to the increased blood viscosity, splenomegaly which observed in 63% of patients, and the occurrence of severe itching on contact with warm bath. Thromboembolic events occurred in 3 patients during the evolution. All patients had the diagnosis of absolute erythrocytosis with moderate hyperleukocytosis and thrombocytosis. Bone marrow biopsy showed hypercellular bone marrow with erythroid and megakaryocytic lineage hyperplasia. The JAK2 V617F mutation was positive with an average allelic load high at 63.1% [22.9 - 93.6]. The dosage of serum EPO was low with an average of 1 mU/ML. During the follow-up period, no patient had progression into acute leukemia or myelofibrosis with myeloid metaplasia, thus no death. The median survival is 49 months [3-99] and the survival without thromboembolic event is 42 months [3-99]. The majority of patients were treated by phlebotomy with 1 or 2 units per month, before starting hydroxy urea. The use of the latter in association with Aspirin (n=10 pts) reduced the use of bloodletting. The thrombotic events required treatment with antithrombotic drug. No patient was treated with Ruxolitinib (treatment not available). Summary/Conclusion: PV remains rare in patients under 55 years of age (17% in our cohort). This has an impact on overall survival and thromboembolic event-free survival with a good prognosis in the young population.