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Polycythemia vera (PV) is a rare blood disorder in which there is an increase in all blood cells, particularly red blood cells. The increase in blood cells makes the blood thicker, leading to strokes or tissue and organ damage. PV patients have an excellent chance of living out a normal life span if properly monitored and treated. A small number of patients may develop acute leukemia or a bone marrow disorder called myelofibrosis.
The causes of PV are still unknown. In 2005, it was discovered that 95 percent of patients with PV have a mutation in the JAK2 gene. This gene plays a significant role in the production of red blood cells (in addition to white blood cells and platelets). When the gene is mutated, there is a loss of normal regulation, and an overproduction of red blood cells, and at times, white blood cells and platelets.
PV is complex and may have many contributing factors. Epidemiologic factors associated with PV include:
- Gender -- Men may be slightly more likely than women to develop the condition.
- Age -- People older than 60 are most likely to develop the condition, though it may occur at any age.
- Environment - Exposure to intense radiation may increase the risk for the condition.
Symptoms of PV may include:
- Fatigue and/or weakness
- Shortness of breath and difficulty breathing while lying down
- Visual disturbance, such as double vision, blurred vision, and blind spots
- Inability to concentrate
- Night sweats
- Flushed complexion
- Bleeding gums
- Excessive menstrual bleeding
- Hemoptysis (coughing up blood)
- Itchy skin, particularly after a hot bath
- High blood pressure
Blood clots also can occur, resulting in a heart attack, stroke, or pulmonary embolism. Liver and spleen enlargement are other potential complications.
PV may be detected on blood tests done for other reasons, before there are any symptoms. Or, doctors may recognize signs of PV during an examination. Additional tests may include:
- Complete blood count - to measure an increase in hemoglobin ( class="st"a protein in red blood cells that carries oxygen), white blood cells and/or platelets in the blood
- Erythropoietin test - a blood test to measure the amount of a hormone called erythropoietin, which tells stem cells in the bone marrow to make more red blood cells
- Genetic testing - to look for mutations to the JAK2 gene
- Bone marrow tests - Your doctor may take a sample of bone marrow tissue to study the increase of precursor cells to platelets, red blood cells, and white blood cells
Treatments for PV can vary depending on a patient's symptoms. Some patients may not need active treatment but should still be monitored by a physician expert. Treatments include:
- Phlebotomy -- a procedure that involves removing blood from the body, can thin the blood to let it flow more easily.
- Low-dose aspirin - may be given to reduce the risk of blood clotting
- Medications - There are no drugs approved by the Food and Drug Administration specifically to treat PV. However, some medicines approved for other diseases are used to treat the signs and symptoms of this condition. They include platelet-lowering medications like hydroxyurea, anagrelide, and interferon, which may be prescribed to reduce the risk of bleeding or clotting complications.
- Radiation - to help suppress overactive bone marrow cells. This therapy helps lower the red blood cell count and keeps blood flow and blood thickness closer to normal.
At Johns Hopkins:
The Johns Hopkins Center for the Chronic Myeloproliferative Disorders coordinates the care of patients with PV and other related disorders and conducts research in these areas.
For more information, see the website for the MPN Research Foundation