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Polycythemia vera

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on November 3, 2022.

Polycythemia vera (PV) is a rare, slow-growing blood cancer.

This disease is a type of myeloproliferative neoplasm (MPN), a term used to describe a number of blood cancers that share similarities. Myeloproliferative neoplasms start with genetic abnormalities to bone marrow cells, changing how they develop and function. Normally, bone marrow cells make all the body’s blood cells in the right amounts.

But with PV, genetic mutations cause the bone marrow to overproduce red blood cells, white blood cells and platelets. Red blood cells carry oxygen throughout the body, while white blood cells fight off infection. Platelets help the blood clot, which helps wounds heal. While these cells play important roles in the body, having too many may lead to medical issues, even death, if left untreated.

PV may lead to complications that may include an increased risk of clotting-related diseases, like a heart attack or stroke.

PV is relatively rare. The National Cancer Institute estimates that between 0.7 to 2.6 new cases of PV are diagnosed per 100,000 people per year in the United States. An estimated 22 people per 100,000 are living with PV, according to the Leukemia and Lymphoma Society.

This overview will cover the basic facts about polycythemia vera including:

Polycythemia vera causes and risk factors

PV typically develops on its own—it isn’t often inherited. Cells in the bone marrow develop genetic mutations that cause PV. Researchers don’t know of any specific reasons that these genetic changes happen.

Factors that place people at a greater risk for developing PV include:

  • Being older: PV is typically diagnosed around age 60. Very rarely, PV can develop in children and young adults.
  • Being male: Men are slightly more likely to develop PV than women.
  • Being Jewish of Eastern European descent: This ethnic group is more likely to develop PV than others of European or Asian descent.

Almost everyone with PV has a genetic mutation in the JAK2 gene, which may cause changes in blood stem cells (called hematopoietic stem cells) that lead to polycythemia vera.

The two specific JAK2 mutations that seem to cause PV are:

  • JAK2 V617F gain-of-function mutation
  • JAK2 exon 12 mutation

The precise role of the JAK2 mutation isn’t fully understood. This gene codes for a protein that makes certain cells grow and divide. When it mutates, this protein is being created all the time, leading the cells to grow out of control and making them live longer than they would normally.

These genetic changes specifically affect hemocytoblasts, which are stem cells that may lead to:

  • Proerythroblasts, which create red blood cells
  • Myeloblasts, which create white blood cells, including neutrophils, basophils or eosinophils
  • Megakaryoblasts, which create platelets

About 16 percent of patients with PV also have a mutation in the TET2 gene, according to the National Library of Medicine. Researchers aren’t sure which role this gene plays.

In rare cases, some people inherit an increased risk of developing PV from their families. PV is passed down in an autosomal dominant manner, which means a person with one copy of the mutated gene is at an increased risk of the disease, and his or her offspring usually has a 50/50 chance of inheriting the broken gene. If these offspring acquire the gene, they have an increased risk of developing PV. This inheritance characteristic indicates a gene mutation that increases the risk, but researchers are unsure of which gene it develops in.

Polycythemia vera symptoms

Early in the disease, PV often doesn’t cause any symptoms. In many cases, it’s first detected during a routine blood test.

Symptoms of PV may include:

  • Dizziness, headaches and tinnitus
  • Vision changes, including double vision, seeing dark spots or blind spots that come and go
  • Feeling pressure or fullness below the ribs on the left side, caused by swelling of the spleen (splenomegaly)
  • Itching, tickling, stinging or burning sensations on the skin, which may occur all over the body or sometimes just on the feet and often appears after being in warm or hot water
  • Redness or purple cast on the ear lobes, nose, cheeks and palms, while the face may look blushed or sunburnt
  • Minor bleeding or bruising
  • Weakness
  • Unintentional weight loss

Some major complications of PV are caused by the increased clotting of the blood. According to the Leukemia & Lymphoma Society, about 30 percent of PV patients have a blood-clotting event before they’re diagnosed with this disease. These events may include:

  • Deep vein thrombosis, which occurs when a clot develops in the deep veins of the legs
  • Pulmonary embolism, which occurs when a clot travels to the lungs and cuts of blood supply
  • Budd-Chiari syndrome, a rare disease in which blood clots narrow the veins that carry blood away from the liver
  • Heart attack
  • Stroke

Without treatment, 40 to 60 percent of patients have blood-clotting complications in the 10 years after diagnosis, according to the Leukemia & Lymphoma Society.

Clotting—often called thrombotic events—is especially dangerous when combined with other underlying risk factors for stroke or heart attack. These may include:

  • Older age
  • Previous clotting events
  • High cholesterol
  • Diabetes
  • Smoking
  • Obesity
  • High blood pressure (hypertension)

As the disease progresses, PV destroys the tissue in the bone marrow, which may cause a more dangerous condition called post-PV myelofibrosis (MF). The more fibrosis in the bone marrow at diagnosis, the more likely post-PV MF will develop, but the less likely it is for a patient to have a clotting event.

And for some patients, PV may progress into acute myeloid leukemia.

Polycythemia vera diagnosis

A diagnosis of polycythemia vera requires many tests. First, a doctor takes a personal history and performs a physical examination. Then, blood tests and a genetic test may be ordered.

Complete blood cell count test (CBC) results that might indicate PV include:

  • Hematocrit (the portion of red blood cells in the blood) levels above 49 percent in men and 48 percent in women, according to the National Cancer Institute (NCI) (Hematocrit is often used to diagnose and monitor treatment response. In healthy men, hematocrit is between 42 and 52 percent, and in women, it’s between 36 and 48.)
  • Hemoglobin (the oxygen and carbon dioxide carrying molecule in the blood) concentration above 16.5 gm/dL in men and 16 g/dL in women, according to the NCI
  • An elevated red blood cell count, which typically gets worse as the disease progresses
  • A mildly elevated white blood cell count, which typically doesn’t get worse as the disease progresses
  • An elevated platelet count, which may get worse during the disease progression
  • Lower than normal levels of the red blood cell-making hormone erythropoietin

The genetic test will check for a JAK2 mutation.

The doctor may also request a biopsy of the bone marrow to determine how healthy it is. A biopsy isn’t required for diagnosis but may be useful for genetic analysis. Patients with PV have higher than normal numbers of blood-forming cells in the bone marrow, and blood tests will show an iron deficiency.

Polycythemia vera treatment

Because polycythemia vera is slow-growing, treatment options aren’t typically aggressive. Treatment is primarily focused on controlling symptoms and preventing complications from clotting.

Treatment may differ based on the risk of these complications and symptoms. It may also vary by the phase of the condition:

  • Low-risk PV patients are those without additional risk factors for stroke or heart attack.
  • High-risk PV includes people over 60 and those who have a history of clotting issues.

PV typically progresses through two phases. In the first phase, called the polycythemic phase, red blood cells form in high numbers, increasing hemoglobin and hematocrit. When the increased production of the polycythemic phase destroys the blood-cell-making tissue of the bone marrow, patients may enter a spent phase, in which some patients may develop post-PV MF.

Post-PV MF occurs when the bone marrow shifts from actively making too many cells to turning fibrotic, which means it’s damaged and scarred. The cells stop making too many red blood cells and eventually make too few, leading to anemia. The spleen keeps swelling, and the bone marrow is scarred from overproducing cells for so long that it can’t produce enough red blood cells or platelets, causing immature white blood cells to form.

Early-phase and low-risk patients are typically started on a regimen of phlebotomy and medications to manage symptoms and complications.

Phlebotomy is a treatment that removes blood from the body. It’s similar to donating blood. Patients go into a clinic, where one unit of blood is removed each week until the number of red blood cells drops. When the number drops, patients need fewer visits to keep the numbers low. The treatment is continued as needed and may be the only treatment needed for some patients for many years.

Daily aspirin (or potentially twice-daily) may be used for pain and to reduce the risk of blood clots, because aspirin makes platelets less likely to stick together.

To manage itching, patients may take antihistamines, selective serotonin reuptake inhibitors or psoralen, which is a medication for psoriasis. Itching may also be eased by light therapy or behavior changes, like adjusting bath water temperature.

If the patient’s platelet count is too high, the medication Agrylin® (anagrelide) may be used to reduce platelet formation without impacting other blood cell counts.

As PV progresses, or if a patient is considered high risk, they may need myelosuppressive drugs. These drugs may reduce red blood cell and platelet numbers by suppressing the blood stem cells, replacing the need for phlebotomy and reducing the risk of clotting. They are used for patients with:

  • High platelet numbers
  • Bleeding or blood clot complications
  • Symptoms that aren’t responding to other treatments

A myelosuppressive drug like Hydrea® (hydroxyurea) may reduce the number of red blood cells made by the bone marrow. The drug reduces both the hematocrit concentration and the platelet count.

Instead of hydroxyurea, some patients may take pegylated interferon (peg-IFN). These may include:

  • Young people who may get pregnant
  • People who aren’t responding to hydroxyurea well
  • Situations where patients can’t continue phlebotomy but don’t have an increased clotting risk

Two other myelosuppressive drugs that may be used are:

  • Jakafi® (ruxolitinib) may reduce red blood cell count and shrink an enlarged spleen. It may be used when a patient develops post-PV myelofibrosis or has prolonged, excessive itching.
  • Busulfan is a drug option that may be recommended for older PV patients.

Polycythemia vera survival rates

PV is slow-growing cancer that’s not typically aggressive but is chronic. PV may usually be managed effectively for long periods, even decades. But it may shorten life expectancy in some patients, and when it does progress, it may be fatal.

According to the National Cancer Institute, survival may be greater than 10 years with treatment. Patients may have a relatively normal quality of life, since treatments for PV don’t typically interfere with daily life or work.

According to a 2016 study in Leukemia and Lymphoma, the five-year survival rate for PV is 79.5 percent based on National Cancer Institute SEER data collected between 2000 and 2012. The researchers also note a median survival with PV of 14 years.

According to a 2021 review article in the journal Leukemia, patients diagnosed with PV who get no treatment will survive around 18 months. Those who are treated with only phlebotomy will survive around four years. With full treatment and regular visits with the doctor, survival rates are improved.

Young patients can survive more than 35 years with PV, though within 20 years of diagnosis, some people progress to other issues:

  • 26% have a major clotting-related event.
  • 16% develop post-PV MF.
  • 4% develop leukemia.

Questions to ask your doctor about PV

People diagnosed with PV often have many questions. Consider asking your doctor or care team these questions to better understand the diagnosis and treatment plan:

  • What do I need to know about PV and surgery?
  • How can we improve my itching?
  • What side effects should I watch out for?
  • How will I know if my PV is progressing?
  • How long does it take for PV to progress?

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