Polycythemia vera (POL-e-si-THEE-me-ah VAY-rah or VE-rah), or PV, is a rare blood disease in which your body makes too many red blood cells.

The extra red blood cells make your blood thicker than normal. As a result, blood clots can form more easily. These clots can block blood flow through your arteries and veins, which can cause a heart attack or stroke.

Thicker blood also doesn't flow as quickly to your body as normal blood. Slowed blood flow prevents your organs from getting enough oxygen, which can cause serious problems, such as angina (an-JI-nuh or AN-juh-nuh) and heart failure. (Angina is chest pain or discomfort.)

Overview

Red blood cells carry oxygen to all parts of your body. They also remove carbon dioxide (a waste product) from your body's cells and carry it to the lungs to be exhaled.

Red blood cells are made in your bone marrow—a sponge-like tissue inside the bones. White blood cells and platelets (PLATE-lets) also are made in your bone marrow. White blood cells help fight infection. Platelets stick together to seal small cuts or breaks on blood vessel walls and stop bleeding.

If you have PV, your bone marrow makes too many red blood cells. It also can make too many white blood cells and platelets.

A mutation, or change, in the body's JAK2 gene is the major cause of PV. This gene makes a protein that helps the body produce blood cells. What causes the change in the JAK2 gene isn't known. PV generally isn't inherited—that is, passed from parents to children through genes.

PV develops slowly and may not cause symptoms for years. The disease often is found during routine blood tests done for other reasons.

When signs and symptoms are present, they're the result of the thick blood that occurs with PV. This thickness slows the flow of oxygen-rich blood to all parts of your body. Without enough oxygen, many parts of your body won't work normally.

For example, slower blood flow deprives your arms, legs, lungs, and eyes of the oxygen they need. This can cause headaches, dizziness, itching, and vision problems, such as blurred or double vision.

Outlook

PV is a serious, chronic (ongoing) disease that can be fatal if not diagnosed and treated. PV has no cure, but treatments can help control the disease and its complications.

PV is treated with procedures, medicines, and other methods. You may need one or more treatments to manage the disease.

Polycythemia vera is a disease in which too many red blood cells are made in the bone marrow.

In polycythemia vera, the blood becomes thickened with too many red blood cells. The number of white blood cells and platelets may also increase. These extra blood cells may collect in the spleen and cause it to swell. The increased number of red blood cells, white blood cells, or platelets in the blood can cause bleeding problems and make clots form in blood vessels. This can increase the risk of stroke or heart attack. In patients who are older than 65 years or who have a history of blood clots, the risk of stroke or heart attack is higher. Patients also have an increased risk of acute myeloid leukemia or primary myelofibrosis.

Primary Polycythemia

Polycythemia vera (PV) also is known as primary polycythemia. A mutation, or change, in the body's JAK2 gene is the main cause of PV. The JAK2 gene makes a protein that helps the body produce blood cells.

What causes the change in the JAK2 gene isn't known. PV generally isn't inherited—that is, passed from parents to children through genes. However, in some families, the JAK2 gene may have a tendency to mutate. Other, unknown genetic factors also may play a role in causing PV.

Secondary Polycythemia

Another type of polycythemia, called secondary polycythemia, isn't related to the JAK2 gene. Long-term exposure to low oxygen levels causes secondary polycythemia.

A lack of oxygen over a long period can cause your body to make more of the hormone erythropoietin (EPO). High levels of EPO can prompt your body to make more red blood cells than normal. This leads to thicker blood, as seen in PV.

People who have severe heart or lung disease may develop secondary polycythemia. People who smoke, spend long hours at high altitudes, or are exposed to high levels of carbon monoxide where they work or live also are at risk.

For example, working in an underground parking garage or living in a home with a poorly vented fireplace or furnace can raise your risk for secondary polycythemia.

Rarely, tumors can make and release EPO, or certain blood problems can cause the body to make more EPO.

Sometimes doctors can cure secondary polycythemia—it depends on whether the underlying cause can be stopped, controlled, or cured.

Polycythemia vera (PV) is a rare blood disease. The disease affects people of all ages, but it's most common in adults who are older than 60. PV is rare in children and young adults. Men are at slightly higher risk for PV than women.

Primary polycythemia (polycythemia vera) can't be prevented. However, with proper treatment, you can prevent or delay symptoms and complications.

Sometimes you can prevent secondary polycythemia by avoiding things that deprive your body of oxygen for long periods. For example, you can avoid mountain climbing, living at a high altitude, or smoking.

People who have serious heart or lung diseases may develop secondary polycythemia. Treatment for the underlying disease may improve the secondary polycythemia. Following a healthy lifestyle to lower your risk of heart and lung diseases also will help you prevent secondary polycythemia.

Polycythemia vera (PV) develops slowly. The disease may not cause signs or symptoms for years.

When signs and symptoms are present, they're the result of the thick blood that occurs with PV. This thickness slows the flow of oxygen-rich blood to all parts of your body. Without enough oxygen, many parts of your body won't work normally.

The signs and symptoms of PV include:

• Headaches, dizziness, and weakness
• Shortness of breath and problems breathing while lying down
• Feelings of pressure or fullness on the left side of the abdomen due to an enlarged spleen (an organ in the abdomen)
• Double or blurred vision and blind spots
• Itching all over (especially after a warm bath), reddened face, and a burning feeling on your skin (especially your hands and feet)
• Bleeding from your gums and heavy bleeding from small cuts
• Unexplained weight loss
• Fatigue (tiredness)
• Excessive sweating
• Very painful swelling in a single joint, usually the big toe (called gouty arthritis)

In rare cases, people who have PV may have pain in their bones.

Polycythemia Vera Complications

If you have PV, the thickness of your blood and the slowed blood flow can cause serious health problems.

Blood clots are the most serious complication of PV. Blood clots can cause a heart attack or stroke. They also can cause your liver and spleen to enlarge. Blood clots in the liver and spleen can cause sudden, intense pain.

Slowed blood flow also prevents enough oxygen-rich blood from reaching your organs. This can lead to angina (chest pain or discomfort) and heart failure. The high levels of red blood cells that PV causes can lead to stomach ulcers, gout, or kidney stones.

Some people who have PV may develop myelofibrosis (MY-e-lo-fi-BRO-sis). This is a condition in which your bone marrow is replaced with scar tissue. Abnormal bone marrow cells may begin to grow out of control.

This abnormal growth can lead to acute myelogenous (my-eh-LOJ-eh-nus) leukemia (AML), a cancer of the blood and bone marrow. This disease can worsen very quickly.

Polycythemia vera (PV) may not cause signs or symptoms for years. The disease often is found during routine blood tests done for other reasons. If the results of your blood tests aren't normal, your doctor may want to do more tests.

Your doctor will diagnose PV based on your signs and symptoms, your age and overall health, your medical history, a physical exam, and test results.

During the physical exam, your doctor will look for signs of PV. He or she will check for an enlarged spleen, red skin on your face, and bleeding from your gums.

If your doctor confirms that you have polycythemia, the next step is to find out whether you have primary polycythemia (polycythemia vera) or secondary polycythemia.

Your medical history and physical exam may confirm which type of polycythemia you have. If not, you may have tests that check the level of the hormone erythropoietin (EPO) in your blood.

People who have PV have very low levels of EPO. People who have secondary polycythemia usually have normal or high levels of EPO.

Specialists Involved

If your primary care doctor thinks you have PV, he or she may refer you to a hematologist. A hematologist is a doctor who specializes in diagnosing and treating blood diseases and conditions.

Diagnostic Tests

You may have blood tests to diagnose PV. These tests include a complete blood count (CBC) and other tests, if necessary.

Complete Blood Count

Often, the first test used to diagnose PV is a CBC. The CBC measures many parts of your blood.

This test checks your hemoglobin (HEE-muh-glow-bin) and hematocrit (hee-MAT-oh-crit) levels. Hemoglobin is an iron-rich protein that helps red blood cells carry oxygen from the lungs to the rest of the body. Hematocrit is a measure of how much space red blood cells take up in your blood. A high level of hemoglobin or hematocrit may be a sign of PV.

The CBC also checks the number of red blood cells, white blood cells, and platelets in your blood. Abnormal results may be a sign of PV, a blood disorder, an infection, or another condition.

In addition to high red blood cell counts, people who have PV also may have high white blood cell and/or platelet counts.

Other Blood Tests

Blood smear. For this test, a small sample of blood is drawn from a vein, usually in your arm. The blood sample is examined under a microscope.

A blood smear can show whether you have a higher than normal number of red blood cells. The test also can show abnormal blood cells that are linked to myelofibrosis and other conditions related to PV.

Erythropoietin level. This blood test measures the level of EPO in your blood. EPO is a hormone that prompts your bone marrow to make new blood cells. People who have PV have very low levels of EPO. People who have secondary polycythemia usually have normal or high levels of EPO.

Bone Marrow Tests

Bone marrow tests can show whether your bone marrow is healthy. These tests also show whether your bone marrow is making normal amounts of blood cells.

The two bone marrow tests are aspiration (as-pi-RA-shun) and biopsy. For aspiration, your doctor removes a small amount of fluid bone marrow through a needle. For a biopsy, your doctor removes a small amount of bone marrow tissue through a larger needle. The samples are then examined under a microscope.

If the tests show that your bone marrow is making too many blood cells, it may be a sign that you have PV.

Polycythemia vera (PV) doesn't have a cure. However, treatments can help control the disease and its complications. PV is treated with procedures, medicines, and other methods. You may need one or more treatments to manage the disease.

Goals of Treatment

The goals of treating PV are to control symptoms and reduce the risk of complications, especially heart attack and stroke. To do this, PV treatments reduce the number of red blood cells and the level of hemoglobin (an iron-rich protein) in the blood. This brings the thickness of your blood closer to normal.

Blood with normal thickness flows better through the blood vessels. This reduces the chance that blood clots will form and cause a heart attack or stroke.

Blood with normal thickness also ensures that your body gets enough oxygen. This can help reduce some of the signs and symptoms of PV, such as headaches, vision problems, and itching.

Studies show that treating PV greatly improves your chances of living longer.

The goal of treating secondary polycythemia is to control its underlying cause, if possible. For example, if the cause is carbon monoxide exposure, the goal is to find the source of the carbon monoxide and fix or remove it.

Treatments To Lower Red Blood Cell Levels

Phlebotomy

Phlebotomy (fle-BOT-o-me) is a procedure that removes some blood from your body. For this procedure, a needle is inserted into one of your veins. Blood from the vein flows through an airtight tube into a sterile container or bag. The process is similar to the process of donating blood.

Phlebotomy reduces your red blood cell count and starts to bring your blood thickness closer to normal.

Typically, a pint (1 unit) of blood is removed each week until your hematocrit level approaches normal. (Hematocrit is the measure of how much space red blood cells take up in your blood.)

You may need to have phlebotomy done every few months.

Medicines

Your doctor may prescribe medicines to keep your bone marrow from making too many red blood cells. Examples of these medicines include hydroxyurea and interferon-alpha.

Hydroxyurea is a medicine generally used to treat cancer. This medicine can reduce the number of red blood cells and platelets in your blood. As a result, this medicine helps improve your blood flow and bring the thickness of your blood closer to normal.

Interferon-alpha is a substance that your body normally makes. It also can be used to treat PV. Interferon-alpha can prompt your immune system to fight overactive bone marrow cells. This helps lower your red blood cell count and keep your blood flow and blood thickness closer to normal.

Radiation Treatment

Radiation treatment can help suppress overactive bone marrow cells. This helps lower your red blood cell count and keep your blood flow and blood thickness closer to normal.

However, radiation treatment can raise your risk of leukemia (blood cancer) and other blood diseases.

Treatments for Symptoms

Aspirin can relieve bone pain and burning feelings in your hands or feet that you may have as a result of PV. Aspirin also thins your blood, so it reduces the risk of blood clots.

Aspirin can have side effects, including bleeding in the stomach and intestines. For this reason, take aspirin only as your doctor recommends.

If your PV causes itching, your doctor may prescribe medicines to ease the discomfort. Your doctor also may prescribe ultraviolet light treatment to help relieve your itching.

Other ways to reduce itching include:

• Avoiding hot baths. Cooler water can limit irritation to your skin.
• Gently patting yourself dry after bathing. Vigorous rubbing with a towel can irritate your skin.
• Taking starch baths. Add half a box of starch to a tub of lukewarm water. This can help soothe your skin.

Experimental Treatments

Researchers are studying other treatments for PV. An experimental treatment for itching involves taking low doses of selective serotonin reuptake inhibitors (SSRIs). This type of medicine is used to treat depression. In clinical trials, SSRIs reduced itching in people who had PV.

Imatinib mesylate is a medicine that's approved for treating leukemia. In clinical trials, this medicine helped reduce the need for phlebotomy in people who had PV. This medicine also helped reduce the size of enlarged spleens.

Researchers also are trying to find a treatment that can block or limit the effects of an abnormal JAK2 gene. (A mutation, or change, in the JAK2 gene is the major cause of PV.)

Polycythemia vera (PV) develops very slowly. It may not cause signs or symptoms for years. If you have PV, the sooner it's diagnosed, the sooner your doctor can begin treating you. With proper treatment, you can prevent or delay complications.

Preventing Complications

Moderate physical activities, such as walking, can safely increase your heart rate and improve blood flow to your body. Improving blood flow lowers your risk of blood clots. Leg and ankle stretching exercises also can help improve your blood flow.

PV may cause itching all over your body. It's important not to scratch and damage your skin. If bathing or showering causes you to have severe itching, try using cooler water and gentler soap. Carefully and gently dry your skin after baths, and use moisturizing lotion on your skin. Starch baths also may help ease itchy skin.

PV causes poor blood flow in your hands and feet. As a result, you may be more prone to injuries from cold, heat, and pressure. If you have PV, avoid long-term exposure to extremes in temperature or pressure. For example:

• Take extra care of your hands and feet in cold weather. Wear warm gloves, socks, and shoes.
• Avoid extreme heat, and protect yourself from the sun. Drink plenty of liquids. Avoid hot tubs, heated whirlpools, or hot baths of any type. Also, tanning beds, sun lamps, and heat lamps can damage your skin if you have PV.
• Guard against trauma or situations where you may be at high risk of injury, such as during sports or strenuous activities. If you're injured, seek treatment right away. Tell the person treating you that you have PV.
• Check your feet regularly and report any sores to your doctor.

Getting Ongoing Care

If you have PV, you'll need lifelong medical care for the disease. Ask your doctor how often you should schedule followup visits.

Routine care will allow your doctor to detect any changes with your PV and treat them early, if needed. You may need periodic blood tests to show whether the disease is getting worse.

Follow your treatment plan and take all of your medicines exactly as your doctor prescribes.