Polycythemia vera (PV) is one of a group of cancers called myeloproliferative neoplasms (or cancers) in which the body produces an excessive amount of red blood cells. Red blood cells are responsible for carrying oxygen to all parts of the body.
Blood is carried throughout the body by a system of veins and arteries. When too many red blood cells exist in your blood, they begin to form clots within the blood vessels. Clots are formed by large amounts of cells grouped together.
Many people with this condition easily ignore early symptoms such as fatigue. Untreated PV, on the other hand, cannot be ignored, as serious symptoms will usually begin to develop due to the blood clots. The clots block blood from reaching the heart or brain, causing serious damage.
There is no known cure for PV, so treatment focuses on using medications to prevent serious blood clots. Unfortunately, people with PV who do not follow treatment regimens have a high likelihood of dying early from clot complications.
Polycythemia vera is a rare disorder that occurs more often in men than in women, and rarely in anyone under 40. PV arises from a mutation in a protein called Janus kinase 2 (JAK2) caused by a gene (JAK2V617F) mutation. In its normal working state, JAK2 protein helps make blood cells, but in a mutated state, it causes an excessive amount of red blood cells. Mutations are changes or damage in the body’s DNA. DNA is responsible for all of your physical characteristics, from eye color to fingerprints. It’s not known what causes the gene mutation but in general, it is not thought to be inheritable (passed down from parents to children).
Red blood cells are made in your bone marrow. This production of blood cells is supposed to be tightly regulated. If you have PV, your bone marrow produces too many red blood cells.
Early symptoms of PV are common physical ailments and can be easily ignored by the patient. However, untreated PV may cause blood clots, which can lead to serious complications.
Early symptoms of PV include:
- difficulty breathing
- tingling in the hands and feet
Significant blood clot complications from untreated PV include:
- heart attack
- deep vein thrombosis (DVT)
Doctors may not discover PV until after a fatal complication has occurred. Fatal complications include:
- ischemic stroke, a stroke caused by loss of blood supply to the brain
- pulmonary embolism, a blood clot in the lung
- hemorrhagic death, death from bleeding which is usually from the stomach or other parts of the digestive tract
If your doctor suspects that you might have PV, they will order a blood test called a complete blood count (CBC). A CBC measures the number of red blood cells, the number of white blood cells, the amount of hemoglobin (a protein that carries oxygen) in the blood, as well as how much space is taken up by red blood cells in the blood. If you have PV, an unusually large percentage of your blood volume will be taken up by red blood cells.
PV is a chronic illness and can’t be cured. The only way to treat the disease is through management and prevention. Doctors will treat patients differently based upon their risk for blood clots.
Patients with a low risk for blood clots include:
- people under 60 without prior history of blood clots
- people with low blood pressure and low cholesterol
- people who do not smoke
Treatments for those at low risk include regular phlebotomy and low-dose aspirin. Phlebotomy is the removal of blood through a vein. Blood is withdrawn daily or almost daily and regular CBCs are run until a decrease in the number of red blood cells is seen. This is basically a wait-and-see approach.
Your doctor may prescribe low-dose aspirin to thin the blood and prevent blood clots. The low-dose aspirin significantly reduces the risk for heart attacks and stroke.
Factors that increase your risk of developing blood clots include:
- a history of prior blood clots
- increasing age
- high blood pressure
High-risk patients may require more specialized treatment, using either hydroxyurea or interferon alpha.
Hydroxyurea suppresses the production of red blood cells. This reduces the risk for clots, but increases the risk of leukemia.
Interferon alpha helps prevent clots but is expensive and has a high risk of fever and flu-like side effects. Patients with thyroid and/or mental disorders are to avoid this medication.
In December 2014, the U.S. Food and Drug Administration approved Jakafi (ruxolitinib) for the treatment of PV. The medication had been previously used to treat myelofibrosis. Doctors prescribe Jakafi to patients who cannot tolerate hydroxyurea or whose blood counts have not responded to hydroxyurea. The medication works by inhibiting growth factors responsible for creating red blood cells and immune system functioning.
PV is a chronic disorder. Treatment works to decrease the amount of red blood cells being produced by the bone marrow and to prevent blood clots from forming. Patients who strictly adhere to treatment may be able to live without complications.