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| DiseaseID |
HGD36 |
| Genetic
Disorder |
POLYCYTHEMIA VERA
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| Gene
Name |
JAK2 gene |
| Description |
Polycythemia vera is a blood disorder in which your bone marrow makes too many red blood cells. Polycythemia vera also may result in production of too many of the other types of cells in your blood — white blood cells and platelets. But, it's the excess red blood cells that thicken your blood and cause most of the health concerns associated with polycythemia vera.
Polycythemia vera — also called primary polycythemia — occurs most often in older adults. It's rare in people younger than 20. Polycythemia vera usually develops very slowly. You may have it for years without noticing any signs or symptoms. Often, polycythemia vera is found during a blood test done for some other reason.
There's no cure for polycythemia vera. To reduce or prevent symptoms and complications from polycythemia vera, treatment focuses on decreasing your number of blood cells. In some cases, polycythemia vera can cause serious complications and, rarely, lead to other blood disorders. But, with proper medical care, many people with polycythemia vera experience few problems related to the disease.
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| Symptoms |
n its early stages, polycythemia vera usually doesn't cause any signs or symptoms. As the disease progresses, you may experience the following polycythemia vera symptoms:
Headache
Dizziness
Itchiness, especially following a warm bath or shower
Redness of your skin
Shortness of breath
Breathing difficulty when you lie down
Numbness, tingling, burning or weakness in your hands, feet, arms or legs
Chest pain
A feeling of fullness or bloating in your left upper abdomen due to an enlarged spleen
Fatigue
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| Causes |
Blood consists of liquid, called plasma, and three types of cells that float within the plasma:
White blood cells. These blood cells fight infection.
Platelets. These blood cells help your blood clot after a cut.
Red blood cells (erythrocytes). These blood cells carry oxygen from your lungs, through your bloodstream, to your brain and your body's other organs and tissues. Your body needs a supply of oxygenated blood to function. Oxygenated blood helps give your body its energy and your skin a healthy glow.
Normally, your body carefully regulates the number of blood cells you have and the ratio of one type to another. But in conditions such as polycythemia vera — called myeloproliferative disorders — the mechanism your body uses to control the production of blood cells becomes impaired, and your bone marrow makes too many or too few of some blood cells.
Mutation causes the disorder
The problem with blood cell production associated with polycythemia vera is caused by a change, or mutation, to DNA in a single cell in your bone marrow. In polycythemia vera, researchers have found this mutation to be a change in a protein switch that tells the cells to grow. Specifically it's a mutation in the protein JAK2 (the JAK2 V617F mutation). More than 90 percent of patients with polycythemia vera, and about half of patients with other myeloproliferative disorders, have this mutation. Doctors and researchers don't understand the full role of this mutation and its implications for treating the disease.
Under normal circumstances, your DNA is a set of instructions for your cells, telling them how and when to grow and divide. The DNA mutation responsible for polycythemia vera makes blood cell production go awry. All the cells produced by that first mutant cell have the same problem, and they dominate your blood cell production. (This type of DNA abnormality is called a clonal disorder.)
The DNA mutation that causes polycythemia vera occurs after conception — meaning that your mother and father don't have it — so it's acquired, rather than inherited from a parent. Researchers and doctors don't know what causes the mutation. |
| Diagnosis |
Blood tests
Doctors most frequently use blood tests to diagnose polycythemia vera. If you have polycythemia vera, blood tests may reveal:
An increase in the number of red blood cells and, in some cases, an increase in platelets or white blood cells.
Elevated hematocrit measurement, the percentage of red blood cells that make up total blood volume.
Elevated levels of hemoglobin, the iron-rich protein in red blood cells that carries oxygen.
Lower than normal levels of oxygen in your blood.
Very low levels of erythropoietin (EPO), a hormone that stimulates bone marrow to produce new red blood cells, because the excess red blood cells turn off the production of EPO by the kidneys.
Bone marrow aspiration or biopsy
If your doctor suspects you have polycythemia vera, he or she may recommend a bone marrow aspiration or biopsy to collect a sample of your bone marrow. A bone marrow biopsy involves taking a sample of solid bone marrow material. A bone marrow aspiration is usually done at the same time as a biopsy. During an aspiration, your doctor withdraws a sample of the liquid portion of your marrow. To help you visualize this, think of your bone marrow as a moist sponge. Aspiration takes the liquid from the sponge. The biopsy takes a piece of the sponge.
If an examination of your bone marrow shows that it's producing higher than normal amounts of blood cells, it may be a sign of polycythemia vera. If you have polycythemia vera, analysis of your bone marrow or blood also may show the DNA change (JAK2 V617F mutation) that's associated with the disease.
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| Treatment |
Polycythemia vera is a chronic condition that can't be cured. Treatment focuses on reducing your amount of blood cells in order to control signs and symptoms of the disease and decrease the risk of complications.
Treatment may include:
Phlebotomy. This is usually the first treatment option for most people with polycythemia vera. Phlebotomy involves drawing a certain amount of blood from one of your veins. This reduces the number of blood cells and decreases your blood volume, making it easier for your blood to function properly. How often you need phlebotomy depends on the severity of your condition.
Medication to decrease blood cells. Phlebotomy alone may not be enough to control the signs, symptoms and complications of polycythemia vera in some people. If this is the case for you, your doctor may prescribe medications such as hydroxyurea or anagrelide to suppress your bone marrow's ability to produce blood cells. Radioactive phosphorus (32p) also can be used to reduce the number of red blood cells. Interferon-alpha may be used to stimulate your immune system to fight the overproduction of red blood cells.
Low-dose aspirin. Your doctor may recommend you take a low dose of aspirin to reduce your risk of blood clots. Low-dose aspirin may also help reduce burning pain in your feet or hands.
Therapy to reduce itching. If you have bothersome itching, your doctor may prescribe medication, such as antihistamines or H-2-receptor blockers, or recommend ultraviolet light treatment to relieve your discomfort.
Researchers are studying treatments for polycythemia vera to block the activated protein JAK2 V617F. Although no treatments with this ability are currently approved by the Food and Drug Administration, these types of polycythemia vera treatments may be available in the future. |
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