What is polycythemia vera (PV)?

PV is a blood disorder in which the body makes too many red blood cells. These extra red cells make blood thicker than normal. The thickened blood flows slower and may clot within your body.

Red blood cells carry oxygen to organs and tissues throughout the body. If the blood moves too slowly or clots, the cells cannot deliver enough oxygen. This situation can cause serious complications including heart attack, stroke, and heart failure.

PV affects about 22 out of every 100,000 people. Doctors diagnose it most commonly in men over 60 years old.

What causes polycythemia vera (PV)?

Doctors classify PV into 2 types. The cause of the condition determines each type.

  • Primary PV occurs when there is a genetic mutation (abnormality). Almost all people diagnosed with PV have a mutation in the JAK2 (Janus kinase) gene. In most cases, PV is not hereditary (passed down through families), but it is hereditary in a few cases. Mutations in the TET2 gene are also found commonly in PV cells.
  • Secondary PV (acquired) occurs in people who experience low levels of oxygen in their blood for long periods of time. This extended lack of oxygen causes the body to make extra amounts of a hormone called erythropoietin (EPO). Too much EPO in the body can cause it to make too many red blood cells.

What are the symptoms of polycythemia vera (PV)?

People with PV experience a variety of symptoms. Some people have no symptoms at all. Symptoms include:

  • Tiredness and weakness
  • Difficulty breathing when lying down
  • Enlarged (bigger than normal) spleen (organ that clears blood cells from the body)
  • Blurry or double vision
  • Itchy skin, especially following a warm bath
  • Skin that is reddish or purplish in color
  • Bleeding gums
  • Weight loss
  • Tinnitus (ringing in the ears)
  • Sweating, especially at night

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