Polycythemia vera: Description, Causes and Risk Factors:
Alternative Names: Osler disease, Osler-Vaquez disease, Vaquez disease, erythremia, polycythemia rubra, polycythemia rubra vera.
Polycythemia vera is a chronic myeloproliferative disorder characterized by an increased red blood cell mass (RCM), or erythrocytosis, which leads to hyperviscosity and an increased risk of thrombosis.
Polycythemia vera results from uncontrolled blood cell production, especially red cells, as a result of acquired mutations in an early blood-forming cell. Because this early cell has the capability to form not only red cells, but also white cells and platelets, any combination of these cell lines may be affected.
The cause of polycythemia vera is not fully understood. Virtually all patients with polycythemia vera have a mutation of the It is usually associated with a gene mutation called JAK2 V617F. The cause of this mutation is unknown. This mutated gene likely plays a role in the onset of polycythemia vera. However, its precise role as the cause of the disease is still under study.
Most patients with polycythemia vera do not have a family history of the disorder. However, occasionally there is more than one family member with the disease. Polycythemia vera is more prevalent among Jews of Eastern European descent than other Europeans or Asians. The incidence varies worldwide, ranging from approximately 0.5 to 2.5 out of 100,000 population. The average age at which polycythemia vera is diagnosed is about 60-65 years. It is uncommon in individuals younger than 30 years of age.
Hematocrit level > 52 percent (0.52) in white men, > 47 percent (0.47) in blacks and women.
- Hemoglobin level > 18 g per dL (180 g per L) in white men, > 16 g per dL (160 g per L) in
More common symptoms:
Blacks and women.
- Pruritus after bathing.
- Weight loss.
Less common symptoms:
- Budd-Chiari syndrome.
- Hemorrhagic events.
- Ischemic digits.
- Thrombotic events.
- Transient neurologic complaints (headache, tinnitus, dizziness, blurred vision, paresthesias).
- Atypical chest pain.
Major diagnostic criteria include increased RCM, normal oxygen saturation, and the presence of splenomegaly. The test for RCM is a nuclear medicine study involving autologous infusion of radio-labeled red blood cells followed by serial phlebotomy to determine distribution. Physicians may refer patients to a specialty laboratory for this study.
Serum erythropoietin (EPO), bone marrow histopathology and karyotype, and the presence of endogenous erythroid colonies (EEC) have been proposed as diagnostic tests for Polycythemia vera. Because polycythemia vera is an autonomous (i.e., EPO-independent) erythroid proliferation, serum EPO levels in polycythemia vera are low or normal.Low-serum EPO levels for polycythemia vera have a sensitivity of 70 percent and a specificity of 90 percent.
The health care provider will perform a physical exam. Tests that may be done include:
Complete blood count with differential.
- Comprehensive metabolic panel.
- Erythropoietin level.
- Genetic test for the JAK2V617F mutation.
- Oxygen saturation of the blood.
- Red blood cell mass.
- Vitamin B12 level.
- Bone marrow biopsy.
This disease may also affect the results of the following tests:
- Lactate dehydrogenase.
- Leukocyte alkaline phosphatase.
- Platelet aggregation test.
- Serum uric acid.
Decisions about the types of therapy for polycythemia vera are based on:
The symptoms and rate of progression of the disease.
- The patient's age.
- The patient's overall health, including any other coexisting diseases.
No single treatment is available for polycythemia vera. Thrombosis accounts for the majority of morbidity and mortality. The major goal of treatment is to prevent thrombotic events. Examples of thrombotic events include arterial and venous thrombosis, cerebrovascular accident, deep venous thrombosis, myocardial infarction, peripheral arterial occlusion, and pulmonary infarct.
The two main initial treatments for polycythemia vera are phlebotomy, the removal of blood from a vein in a manner similar to a blood donation, and drug therapy to lower the platelet count, if it is high. Drug therapy may be combined with phlebotomy or replace phlebotomy as a treatment to control the hematocrit or hemoglobin concentration, if phlebotomy is insufficient to do so.
Researchers continue to look for more effective ways to treat polycythemia vera by conducting clinical trials (research studies) of new therapies or combinations of therapies. Some treatments under examination for polycythemia vera in clinical trials include:
Imatinib mesylate (Gleevec®): This drug, approved for use in the treatment of chronic myelogenous leukemia, is currently being studied in the treatment of polycythemia vera to evaluate its effectiveness in reversing the overproduction of red cells. It is possible that this drug may be able to inhibit the process responsible for the overproduction by blocking certain enzymes needed for red cell growth.
Allogeneic stem cell transplantation: Small numbers of younger polycythemia vera patients with myelofibrosis, splenomegaly (enlarged spleen), or progressive disease including myelodysplastic syndrome or acute myeloid leukemia, may be candidates for allogeneic stem cell transplantation. One clinical trial currently under way is studying the effectiveness of combining low-dose total-body radiation therapy and fludarabine (Fludara®) with alemtuzumab (Campath®) followed by allogeneic stem cell transplantation in treating patients who have severe progressive PV, other myeloproliferative disorders or myelodysplastic syndrome. Alemtuzumab is a type of monoclonal antibody therapy.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.