Polycythemia vera

[Jessica]

Polycythemia vera is a myeloproliferative neoplasm of the blood-producing cells of the bone marrow that results in overproduction of all types of blood cells.

Polycythemia vera is due to mutations in the Janus kinase 2 (JAK2) gene, which produces a protein (enzyme) that stimulates excessive production of blood cells.
People may feel tired and weak, light-headed, or short of breath, or develop symptoms caused by blood clots.
Blood tests are done for diagnosis.
Phlebotomy is done to remove excess red blood cells, and some people take aspirin and sometimes other drugs.

In a myeloproliferative neoplasm, the blood-producing cells in the bone marrow (precursor cells, also called stem cells) develop and reproduce excessively.
Polycythemia vera involves increased production of all types of blood cells: red blood cells, white blood cells, and platelets. Increased production of red blood cells is termed erythrocytosis. Sometimes people with polycythemia vera have only increased red blood cell production, but usually increased red blood cell production by itself is due to another cause.
In polycythemia vera, the excess of red blood cells increases the volume of blood and makes it thicker, so that it flows less easily through small blood vessels.
Polycythemia vera occurs in about 2 in every 100,000 people. The average age at which the disorder is diagnosed is 60, but it also occurs in people younger than 40. More men than women develop polycythemia vera over age 60, but more women than men develop the disease under age 40.