What is polycythemia vera?

Related conditions:
Essential thrombocythemia, idiopathic myelofibrosis

Definition:
Polycythemia vera is a rare myeloproliferative disorder that causes chronic overproduction of red blood cells and possibly of 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 in 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. Although family history is not a risk factor, polycythemia vera occasionally occurs in more than one family member.

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 may lead to acute myelogenous leukemia (AML), an aggressive disease characterized by overabundance in blood and bone marrow of immature white blood cells.

Incidence: The reported incidence ranges from 0.5 to 2.5 per 100,000 people worldwide.

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, 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, presence of the JAK2 mutation in blood cells, or low erythropoietin (EPO) level (determined by assay).

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. 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.

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"Polycythemia Vera." Merck Manual. Merck, Apr. 2014. Web. 11 Dec. 2014.

"What Is Polycythemia Vera?" National Heart, Lung, and Blood Institute. Natl. Inst. of Health, 1 Mar. 2011. Web. 11 Dec. 2014.