Polycythemia Vera

Polycythemia vera, or PV, is a rare blood disease in which the body makes too many red blood cells. These extra red blood cells make blood thicker than normal. The thickened blood flows more slowly through small blood vessels and can form clots. These clots can cause heart attack and stroke.

Symptoms

Polycythemia vera (PV) develops very slowly. You may not see signs and symptoms of PV for years after you have the condition. The signs and symptoms of PV are the result of the thickness of blood. This slows the flow of blood and the oxygen blood carries to all parts of your body. Without enough oxygen, the parts of your body can have problems functioning normally.

The most common signs and symptoms of PV include headache, dizziness, weakness, shortness of breath, difficulty breathing when you’re lying down, feelings of pressure or fullness on the left side of the abdomen due to enlargement of the spleen, double or blurred vision, blind spots, itching all over (especially after a warm bath), reddened face, burning sensation in your skin (especially your hands and feet), bleeding from your gums, more than normal bleeding from small cuts, and unexplained weight loss. In rare cases, you may experience pain in your bones if you have PV.

Possible Complications

If you have PV, the thickness of your blood and slower blood flow can create serious health problems. The most serious complication is that it may cause blood to form clots. Blood clots can cause you to suffer a heart attack or stroke. They also can cause liver and spleen to enlarge. Blood clots in the liver and spleen can cause sudden and intense pain. The high levels of red blood cells that cause PV can lead to stomach ulcers, gout, or kidney stones.

Diagnosis

You may have polycythemia vera (PV) before signs or symptoms appear. Many times, doctors discover their patients have PV through routine blood tests performed for other reasons. If you have no clear symptoms for PV, but show higher than normal levels of hemoglobin and hematocrit in your blood test, your doctor may want to do more tests.

Doctors diagnose PV based on symptoms, physical exam, age, test results, and overall health, including other chronic diseases. The doctor will find out as much as possible about your medical history. Your doctor will look for signs of polycythemia during your physical exam, including enlargement of the spleen, reddened skin on the face, and bleeding from the gums. If your doctor confirms that you have polycythemia, the next step is to determine if you have PV or secondary polycythemia.

Often, your medical history and physical exam can confirm which type of polycythemia you have. If not, your doctor may order tests that check the level of erythropoietin (EPO) in your blood. Patients with PV have extremely low levels of EPO. Patients with normal to high levels of EPO in their blood more than likely suffer from secondary polycythemia.

Diagnostic Tests and Procedures

The doctor may order a number of different blood tests to diagnose PV. These tests include a complete blood count (CBC), conducted along with other tests if necessary.

The CBC counts the numbers of all three types of blood cells—red blood cells that carry oxygen, white blood cells that fight infection, and platelets that help clot the blood. If your CBC shows higher than normal counts of these cells, especially the red blood cells, you may have PV.
The CBC also measures hemoglobin, the iron-rich protein in red blood cells that carries oxygen through the body. A higher than normal hemoglobin level may be a sign that you have PV.
The hematocrit part of the CBC measures the percentage of blood that consists of red blood cells. A higher than normal hematocrit level may be a sign that you have PV.

The doctor may order additional blood tests to confirm a diagnosis of PV:

A blood smear—A sample of your blood is viewed under a microscope to collect information about the number and shape of blood cells. Your doctor will examine the smear for the high concentration of red blood cells seen in PV and for abnormal types of blood cells that are seen in myelofibrosis and other conditions related to PV.
Arterial blood gas test—A sample of your blood is taken from an artery to measure the amount of oxygen, carbon dioxide, and pH (acidity) in the blood. If your test results show a lower than normal level of oxygen in your blood, it may be a sign you have PV.
EPO level—Your blood is tested to measure the level of EPO, a hormone that stimulates bone marrow to produce new blood cells. If you have PV, this test result will show lower than normal levels of EPO in your blood.
Red blood cell mass—This test usually takes place in a hospital in the nuclear medicine department. The health professional performing the test takes a sample of your blood. A very weak radioactive dye is mixed with your blood sample. The weak dye attaches itself to the red blood cells and plasma in your sample. The tagged cells in your sample are injected back into your bloodstream and spread quickly throughout your body. By taking another sample of your blood, or using special cameras sensitive to the dye, technicians can figure out the total number of red blood cells in your body. Higher than normal red blood cell counts may be a sign you have PV.

In some cases, your doctor may want to do a bone marrow biopsy or aspiration. A bone marrow biopsy is a minor surgical procedure your doctor performs to remove a small amount of bone marrow tissue with a needle from your body. In a bone marrow aspiration, your doctor removes a small amount of bone marrow fluid through a needle. Bone marrow biopsy or aspiration tests whether your bone marrow is healthy and producing a normal amount of blood cells. If the test shows that your bone marrow is producing higher than normal amounts of blood cells, it may be a sign you have PV.

Causes

Polycythemia vera (PV) is also known as primary polycythemia which is caused by mutations in the JAK 2 gene. The JAK 2 gene produces an important protein involved in blood production. Doctors and researchers do not know what causes the JAK 2 gene to change. The mutation of the JAK 2 gene occurs after conception. It is not passed from parent to child. The mutation of the JAK 2 gene cannot be reversed.

There is another kind of polycythemia not related to the JAK 2 gene. This is called secondary polycythemia. It is caused by long-term exposure to low levels of oxygen. Long-term lack of oxygen can cause your body to produce more of the hormone erythropoietin (EPO). EPO increases the production of red blood cells above normal levels, leading to thickening of the blood as in PV. People who smoke, spend long hours at high altitudes (such as mountaineers and pilots), or have severe lung or heart disease may develop secondary polycythemia. In some cases, secondary polycythemia can be cured, depending on whether the underlying cause can be controlled or cured.

Reference:

National Heart, Lung, and Blood Institute, USA.