Polycythemia vera (pol-e-sy-THEE-me-uh VEER-uh) is a type of blood cancer. It causes your bone marrow to make too many red blood cells. These excess cells thicken your blood, slowing its flow, which may cause serious problems, such as blood clots.

Polycythemia vera is rare. It usually develops slowly, and you might have it for years without knowing. Often the condition is found during a blood test done for another reason.

Without treatment, polycythemia vera can be life-threatening. But proper medical care can help ease signs, symptoms and complications of this disease.

Many people with polycythemia vera don't have noticeable signs or symptoms. Some people might develop vague symptoms such as headache, dizziness, fatigue and blurred vision.

More-specific symptoms of polycythemia vera include:

• Itchiness, especially after a warm bath or shower
• Numbness, tingling, burning, or weakness in your hands, feet, arms or legs
• A feeling of fullness soon after eating and bloating or pain in your left upper abdomen due to an enlarged spleen
• Unusual bleeding, such as a nosebleed or bleeding gums
• Painful swelling of one joint, often the big toe
• Shortness of breath and difficulty breathing when lying down

When to see a doctor

Make an appointment with your doctor if you have signs or symptoms of polycythemia vera.

Polycythemia vera occurs when a mutation in a gene causes a problem with blood cell production. Normally, your body regulates the number of each of the three types of blood cells you have — red blood cells, white blood cells and platelets. But in polycythemia vera, your bone marrow makes too many of some of these blood cells.

The cause of the gene mutation in polycythemia vera is unknown, but it's generally not inherited from your parents.

Polycythemia vera can occur at any age, but it's more common in adults between 50 and 75. Men are more likely to get polycythemia vera, but women tend to get the disease at younger ages.

Possible complications of polycythemia vera include:

• Blood clots. Increased blood thickness and decreased blood flow, as well as abnormalities in your platelets, raise your risk of blood clots. Blood clots can cause a stroke, a heart attack, or a blockage in an artery in your lungs or a vein deep within a leg muscle or in the abdomen.
• Enlarged spleen. Your spleen helps your body fight infection and filter unwanted material, such as old or damaged blood cells. The increased number of blood cells caused by polycythemia vera makes your spleen work harder than normal, which causes it to enlarge.
• Problems due to high levels of red blood cells. Too many red blood cells can lead to a number of other complications, including open sores on the inside lining of your stomach, upper small intestine or esophagus (peptic ulcers) and inflammation in your joints (gout).
• Other blood disorders. In rare cases, polycythemia vera can lead to other blood diseases, including a progressive disorder in which bone marrow is replaced with scar tissue, a condition in which stem cells don't mature or function properly, or cancer of the blood and bone marrow (acute leukemia).

Your doctor will take a detailed medical history and perform a physical exam.

Blood tests

If you have polycythemia vera, blood tests might reveal:

• More red blood cells than normal and, sometimes, an increase in platelets or white blood cells
• A greater percentage of red blood cells that make up total blood volume (hematocrit measurement)
• Elevated levels of the iron-rich protein in red blood cells that carries oxygen (hemoglobin)

Bone marrow aspiration or biopsy

If your doctor suspects that you have polycythemia vera, he or she might recommend collecting a sample of your bone marrow through a bone marrow aspiration or biopsy.

A bone marrow biopsy involves taking a sample of solid bone marrow material. A bone marrow aspiration is usually done at the same time. During an aspiration, your doctor withdraws a sample of the liquid portion of your marrow.

Specific gene testing

If you have polycythemia vera, analysis of your bone marrow or blood might show the gene mutation that's associated with the disease.

There's no cure for polycythemia vera. Treatment focuses on reducing your risk of complications. These treatments may also ease your symptoms.

Blood withdrawals

The most common treatment for polychythemia vera is having frequent blood withdrawals, using a needle in a vein (phlebotomy). It's the same procedure used for donating blood.

This decreases your blood volume and reduces the number of excess blood cells. How often you need to have blood drawn depends on the severity of your condition.

Treatments to reduce itching

If you have bothersome itching, your doctor may prescribe medication, such as antihistamines, or recommend ultraviolet light treatment to relieve your discomfort.

Medications that are normally used to treat depression, called selective serotonin reuptake inhibitors (SSRIs), helped relieve itching in clinical trials. Examples of SSRIs include paroxetine (Brisdelle, Paxil, Pexeva, others) or fluoxetine (Prozac, Sarafem, Selfemra, others).

Drugs that reduce the number of red blood cells

If phlebotomy alone doesn't help enough, your doctor may suggest medications that can reduce the number of red blood cells in your bloodstream. Examples include:

• Hydroxyruea (Droxia, Hydrea)
• Interferon alfa-2b (Intron A)
• Ruxolitinib (Jakafi)
• Busulfan (Busulfex, Myleran)

Heart medications

Your doctor will also likely prescribe medications to control risk factors for heart and blood vessel disease, including high blood pressure, diabetes and abnormal cholesterol.

Your doctor may recommend that 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.

You can take steps to help yourself feel better if you've been diagnosed with polycythemia vera. Try to:

• Exercise. Moderate exercise, such as walking, can improve your blood flow. This helps decrease your risk of blood clots. Leg and ankle stretches and exercises also can improve your blood circulation.
• Avoid tobacco. Using tobacco can cause your blood vessels to narrow, increasing the risk of heart attack or stroke due to blood clots.
• Avoid low-oxygen environments. Living at high altitudes, skiing or climbing in mountains all reduce the oxygen levels in your blood even further.

• Be good to your skin. To reduce itching, bathe in cool water, use a gentle cleanser and pat your skin dry. Adding starch, such as cornstarch, to your bath might help. Avoid hot tubs, heated whirlpools, and hot showers or baths.

  Try not to scratch, as it can damage your skin and increase the risk of infection. Use lotion to keep your skin moist.

• Avoid extreme temperatures. Poor blood flow increases your risk of injury from hot and cold temperatures. In cold weather, always wear warm clothing, particularly on your hands and feet. In hot weather, protect yourself from the sun and drink plenty of liquids.
• Watch for sores. Poor circulation can make it difficult for sores to heal, particularly on your hands and feet. Inspect your feet regularly and tell your doctor about any sores.

You're likely to start by seeing your primary care physician. If you're diagnosed with polycythemia vera, you might be referred to a doctor who specializes in blood conditions (hematologist).

Here's some information to help you get ready for your appointment.

What you can do

Make a list of:

• Your symptoms, including any that seem unrelated to the reason for which you scheduled the appointment, and when they began
• Key personal information, including other medical conditions and family medical history
• All medications, vitamins or supplements you take, including doses
• Questions to ask your doctor

For polycythemia vera, questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• What tests do I need?
• Is this condition temporary, or will I always have it?
• What treatments are available, and which do you recommend?
• I have other health conditions. How can I best manage them together?
• Should I see a specialist?
• Will I need follow-up visits? If so, how often?
• Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions you think of during the appointment. Take a family member or friend along, if possible, to help you remember the information you're given.

What to expect from your doctor

Your doctor is likely to ask you questions, including:

• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• Does anything worsen your symptoms?