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. Often, excess white blood cells and platelets are also produced. PCV is classified as a myeloproliferative disease. Symptoms include headaches and vertigo, and signs on physical examination include an abnormally enlarged spleen and/or liver. In some cases, affected individuals may have associated conditions including high blood pressure or formation of blood clots. Transformation to acute leukemia is rare. Phlebotomy is the mainstay of treatment. A hallmark of polycythemia is an elevated hematocrit, with Hct > 55% seen in 83% of cases. A somatic (non-hereditary) mutation (V617F) in  the JAK2 gene, also present in other myeloproliferative disorders, is found in 95% of cases.Primary familial polycythemia, also known as primary familial and congenital polycythemia (PFCP), exists as a benign hereditary condition, in contrast with the myeloproliferative changes associated with acquired PCV. In many families, PFCP is due to an autosomal dominant mutation in the EPOR erythropoietin receptor gene. PFCP can cause an increase of up to 50% in the oxygen-carrying capacity of the blood; skier Eero Mäntyranta had PFCP, which is considered to have given him a large advantage in endurance events. Secondary polycythemia
Secondary polycythemia is caused by either natural or artificial increases in the production of erythropoietin, hence an increased production of erythrocytes. In secondary polycythemia,  6 to 8 million and occasionally 9 million erythrocytes may occur per cubic millimeter of blood.
Relative polycythemia
Relative polycythemia is an apparent rise of the erythrocyte level in the blood; however, the underlying cause is reduced blood plasma (hypovolemia, cf. dehydration). Relative polycythemia is often caused by loss of body fluids, such as through burns, dehydration, and stress. A specific type of relative polycythemia is Gaisböck syndrome. In this syndrome, primarily occurring in obese men, hypertension causes a reduction in plasma volume, resulting in (amongst other changes) a relative increase in red blood cell count. Symptoms
Doctors say that patients may not experience in any notable symptom of PV until the late stages. Although vague, these symptoms might help patients get help in the early years of the progression. Severe headache
Dizziness, fatigue, and tiredness
Unusual bleeding, nosebleeds
Pain
Itchiness
Numbness or tingling in different body parts

Notable people
Polycythemia is linked to increased performance in endurance sports due to the blood being able to store more oxygen. It can also be linked to damage from smoking. Eero Mäntyranta, Finnish cross-country skier
Bob Newhart, American comedian

See also
Cytopenia, a decrease in blood cell count
Capillary leak syndrome, another cause of hemoconcentration

References


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