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Primary polycythemia, often called polycythemia vera (PCV), polycythemia rubra vera (PRV), or erythremia, occurs when excess red blood cells are produced as a result of an abnormality of the bone marrow and occasionally in the kidneys. Often, excess non-lymphoid white blood cells and platelets are also produced. Polycythemia vera is classified as a myeloproliferative disease.
Polycythemia vera occurs in all age groups (including children),[1] although the incidence increases with age. One study found the median age at diagnosis to be 60 years,[2] while a study in Olmsted County, Minnesota found that the highest incidence was in people aged 70–79 years.[3] The overall incidence in the Minnesota population was 1.9 per 100,000 person-years, and the disease was more common in men than women.[3] A cluster around a toxic site was confirmed in northeast Pennsylvania in 2008. [4]
Patients with polycythemia vera can be asymptomatic.[5] A classic symptom of polycythemia vera is pruritis, particularly after exposure to warm water, which may be due to abnormal histamine release[6][7] or prostaglandin production.[8] Such itching is present in approximately 40% of patients with polycythemia vera.[2] Gouty arthritis may be present in up to 20% of patients.[2] Peptic ulcer disease is also common in patients with polycythemia vera; the reasons for this are unclear, but may be related to an increased susceptibility to infection with the ulcer-causing bacterium H. pylori.[9]
A rare but classic symptom of polycythemia vera (and the related myeloproliferative disease essential thrombocythemia) is erythromelalgia.[10] This is a sudden, severe burning pain in the hands or feet, usually accompanied by a reddish or bluish coloration of the skin. Erythromelalgia is caused by an increased platelet count or increased platelet “stickiness”, resulting in the formation of tiny blood clots in the vessels of the extremity; it responds rapidly to treatment with aspirin.[11][12]
Patients with polycythemia vera are prone to the development of blood clots (thrombosis). A major thrombotic complication (e.g. heart attack, stroke, deep venous thrombosis, or Budd-Chiari syndrome) may sometimes be the first symptom or indication that a person has polycythemia vera.
Patients with polycythemia vera may often be asymptomatic. Physical exam findings are non-specific, but may include enlarged liver or spleen, plethora, or gouty nodules. The diagnosis is often suspected on the basis of laboratory tests. Common findings include an elevated hemoglobin level or hematocrit, reflecting the increased number of red blood cells; the platelet count or white blood cell count may also be increased. Because polycythemia vera results from an essential increase in erythrocyte production, patients have a low erythropoietin (EPO) level.
In primary polycythemia, there may be 8 to 9 million and occasionally 11 million erythrocytes cubic millimeter of blood (a normal range for adults is 4-6), and the hematocrit may be as high as 70 to 80%. In addition, the total blood volume sometimes increases to as much as twice normal. The entire vascular system can become markedly engorged with blood, and circulation times for blood throughout the body can increase up to twice the normal value. The increased numbers of erythrocytes can cause the viscosity of the blood to increase as much as five times normal. Capillaries can become plugged by the very viscous blood, and the flow of blood through the vessels tends to be extremely sluggish.
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