Polycythemia vera
Polycythemia vera (PV) is a rare myeloproliferative disorder characterized by the chronic overproduction of red blood cells, and potentially white blood cells and platelets, leading to increased blood viscosity. This condition can result in serious complications such as blood clots, heart attacks, strokes, and reduced oxygen supply to various organs, which may impair muscle and lung function. PV predominantly affects older men and individuals of Eastern European Jewish descent, with a higher risk in those carrying a mutation in the JAK2 gene. The exact cause of PV remains unknown, but it typically progresses slowly with symptoms that may include fatigue, headache, dizziness, and itching. Diagnosis often occurs through routine blood tests that reveal elevated hematocrit levels, among other indicators. While there is no cure for PV, treatments like phlebotomy and medication can help manage symptoms and reduce the risks associated with the disorder. Continuous monitoring and treatment can lead to a normal life expectancy and quality of life for those affected.
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Subject Terms
Polycythemia vera
ALSO KNOWN AS: PV
RELATED CONDITIONS: Essential thrombocythemia, idiopathic myelofibrosis
DEFINITION: Polycythemia vera is a rare myeloproliferative disorder that causes chronic overproduction of red blood cells and possibly white cells and platelets. Although these cells function normally, their overabundance causes increased blood viscosity and decreased blood flow, with possible clot formation and resultant heart attack or stroke, and possible systemic decreases in oxygen supply, resulting in compromised muscle function, lung function, and visual acuity, or angina, congestive heart failure, or gout.
Risk factors: Polycythemia vera occurs more frequently in men aged sixty and older and in Jews of Eastern European descent. People with a JAK2 mutation are at a higher risk as well. Although family history is not a risk factor, polycythemia vera occasionally occurs in more than one family member. Polycythemia vera occurs in people exposed to intense radiation or toxic substances.
Etiology and the disease process: The cause of polycythemia vera is unknown. Disease progression is slow, as is symptom onset. Polycythemia vera occurs because of a deoxyribonucleic acid (DNA) mutation, in most cases, in the JAK2 gene in hematopoietic stem cells (blood-forming cells in bone marrow) that triggers blood cell overproduction.
In rare instances, myelofibrosis abnormal, fibrous bone marrow tissue may develop and lead to acute myelogenous leukemia (AML), an aggressive disease characterized by overabundance of immature white blood cells in blood and bone marrow.
Incidence: The Leukemia and Lymphoma Society estimates the incidence of newly diagnosed cases of polycythemia vera is between 0.01 and 2.61 per 100,000 annually.
Symptoms: Overabundance of red blood cells and platelets causes the symptoms associated with polycythemia vera. Symptoms may include dizziness, enlarged spleen, fatigue, headache, itchy or flushed skin, kidney stones, profuse sweating, shortness of breath, bloating, nose bleeds, stomach ulcers, tinnitus, and vision problems.
Screening and diagnosis: Due to its slow progression and delayed expression of nonspecific symptoms, polycythemia vera may be diagnosed via routine blood testing if results indicate a 33 percent or greater increase in hematocrit level, hemoglobin concentration, and red cell count. Other indicators may be elevated platelet count or white cell count, the presence of the JAK2 mutation in blood cells, or low erythropoietin (EPO) level (determined by assay). Bone marrow biopsy to determine if the number of blood cells is high and molecular tests that look for abnormalities in genes, chromosomes, and proteins may also be used.
Treatment and therapy: Initial options are phlebotomy to reduce blood volume and drug therapy to decrease cell count. The platelet count-lowering drug anagrelide, or the myelosuppressive drugs hydroxyurea, interferon alpha, and radioactive phosphorus (32P) may be used. The JAK2 inhibitor ruxolitinib may also be used. However, side effects are associated with all treatments, including phlebotomy, which can result in anemia.
Prognosis, prevention, and outcomes: There is no cure for polycythemia vera. If untreated, it can lead to death. If treated, life expectancy and quality of life may be unaffected. Response to therapy may be monitored via hematocrit levels and hemoglobin concentrations.
Bibliography
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“Polycythemia Vera.” Johns Hopkins Medicine, www.hopkinsmedicine.org/health/conditions-and-diseases/polycythemia-vera. Accessed 19 June 2024.
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Polycythemia Vera Facts. Leukemia and Lymphoma Society, Apr. 2015, www.lls.org/sites/default/files/file‗assets/FS13‗PolycythemiaVera‗FactSheet‗final5.1.15.pdf. Accessed 24 Jan. 2018.
“Treatment.” Leukemia & Lymphoma Society, www.lls.org/myeloproliferative-neoplasms/polycythemia-vera/treatment. Accessed 19 June 2024.
"What Is Polycythemia Vera?" National Heart, Lung, and Blood Institute, National Institutes of Health, 1 Mar. 2011, www.nhlbi.nih.gov/health-topics/polycythemia-vera. Accessed 11 Dec. 2014.