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Myeloproliferative neoplasms (MPN) are the group of clonal, malignant hematopoietic stem cell disorders, characterized by the proliferation of one or more blood lines with normal or nearly normal maturing in the bone marrow and in extramedullar hematopoietic organs. Hemorrhagic syndrome is a complication that occurs in about a quarter of patients with PV and even 60% of patients with ET. Bleeding may complicate the clinical course of the IMF. It is manifested in the form of petechiae and ecchymoses, or may be life-threatening as uncontrolled esophageal bleeding. Bleeding occurs due to ineffective megakaryocytopoiesis, retention of platelets in the large spleen, qualitative platelet disorders, acquired deficiency of factors V and vWF, disseminated intravascular coagulation.

The aim of this study is to monitor the count of erythrocytes, leukocytes and platelets, as well as hemoglobin and hematocrit values as potential risk factors for the incidence of hemorrhagic complications in patients with chronic myeloproliferative neoplasms.

During the three-year period we monitored the occurrence of hemorrhagic complications in 139 patients of both sexes, aged between 30 and 87 years, being diagnosed with Ph-myeloproliferative neoplasm. Patients were classified into the following groups: 1. Group with polycythemia vera (PV) (61); 2. Group with essential thrombocythemia (ET) (28); 3. Group with idiopathic myelofibrosis (IMF) (25); 4. Group with unclassified myeloproliferative neoplasm (MPNs) (25). The following possible risk factors were monitored: counts of erythrocytes, leukocytes and platelets, as well as hemoglobin and hematocrit values. We used methods of clinical, laboratory, endoscopy, ultrasound and CT scans.

The highest percentage of hemorrhagic complications were in the group of patients with ET and IMF (p<0,01), followed by the group with MPNs (p<0,05). In all three groups, the incidence of hemorrhagic complications in patients older than 65 years of age was higher (p<0,001). The erythrocyte count ranged from 6,45-8,89 x 10¹²/, leukocyte count 1,2-27,1 x 10⁹/L and the platelet count ranged from 10,2 -1986,5 x 10⁹/L. Hemoglobin values ranged from 176-210 g/L, and hematocrit from 0.58 to 0.83 L/L. The highest erythrocyte count, the highest hemoglobin and hematocrit values, as well as the highest leukocyte count was recorded in the group of patients with PV and MPNs (p <0,001) and the lowest in the group of patients with IMF (p <0,01). Among the group of patients with ET and MPNs there was no statistically significant difference in those parameters. In the group of patients with PV and MPNs hemorrhagic complications were more frequent in percentage in patients with leukocytosis and erythrocytosis, but without statistical significance. The highest platelet count was found in the group of patients with ET and MPNs (p<0,001), and the lowest in the group of patients with IMF (p<0,01). Among the group of patients with PV and MPNs there was no statistically significant difference with regard to platelet count. Hemorrhagic complications were more frequent both in patients with platelet count below 10x10⁹/L (p<0,05) and in patients with platelet count over 1000x10⁹/L (p<0,01). The increase in platelet count influences the adsorption of larger von Willebrand multimers on the platelet membrane, thus having an effect on their elimination from circulation and degradation.

The platelet count can be considered a significant parameter for monitoring the risk of hemorrhagic complications in patients with myeloproliferative neoplasms, particularly with ET and IMF. Deviation from the count of leukocytes, erythrocytes, hemoglobin and hematocrit values may be considered as a potential risk factor for bleeding in patients with myeloproliferative neoplasms, but further follow-up and a larger number of subjects are needed. The age of the patient can also be considered as a risk factor for the incidence of hemorrhagic syndrome in those patients. The follow-up of patients with unclassified myeloproliferative neoplasms has been particularly important, which showed a high prevalence of hemorrhagic complications, and with the purpose of their further differentiation.