The word polycythemia simply means "many cells in the blood." There are two forms of this disease: polycythemia vera and secondary polycythemia.
Polycythemia vera (also called primary polycythemia) is a rare growth disorder of the bone marrow, occurring when the marrow is overactive and produces more blood cells than the body needs.
Secondary polycythemia affects some people as a result of limited oxygen due to smoking or living at high altitudes.
Polycythemia vera usually produces a high concentration of red blood cells or hemoglobin in the circulating blood, but it's important to note that white blood cell and platelet counts may also be increased.
Polycythemia vera stems from problems with the bone marrow. Bone marrow is found in the centre of most bones and normally produces all red blood cells and platelets and most white blood cells. When this process breaks down, production of cells is no longer orderly and conditions such as polycythemia can result. Although the exact cause of polycythemia vera is unknown, researchers have found that a specific gene mutation is associated with almost all people with this condition.
Polycythemia vera is a rare condition usually affecting men in their 60s. It is more common in men than in women. The condition is rarely seen in people under age 40, but can also affect babies.
Although the cause of polycythemia vera is unknown, a number of factors are involved that appear to lead to secondary polycythemia. A high content of red blood cells builds up in response to low oxygen concentration in the air. Because there's less oxygen in the blood, the body attempts to overcome the lack by making more red blood cells. It doesn't stop, however, and keeps producing them until there are too many. The bone marrow can also be overstimulated by testosterone replacement therapy.
Living for long periods at high altitudes where there's less oxygen may lead to polycythemia. It also may occur in people with chronic lung conditions and certain kidney tumours and cysts. Heavy smoking is associated with an increase in carbon monoxide in the blood and may also lead to higher red cell and hemoglobin levels. Low blood oxygen levels (hypoxia) due to congenital heart disease also appear to be a factor in the development of polycythemia.
Most people who live at high altitudes don't appear to suffer secondary polycythemia. In fact, the condition is virtually absent in some mountain regions. When it does occur, it's thought that other environmental factors, such as smoking or mining, may contribute.
Polycythemia in babies usually occurs because the baby receives more than the normal amount of blood from the placenta during birth. It also can result from the mother living at a high altitude, or if the baby had a placenta that was not functioning optimally.
Symptoms and Complications
Polycythemia may not cause any symptoms. It's often discovered only if a hemoglobin test or a red blood cell count is done. Some people do experience symptoms that appear gradually. These may include itching following bathing, dizziness, and a flushing of the face and hands. Weakness, headaches, visual disturbances, and a sense of "fullness" in the head and in the left upper abdomen may also be associated with the condition. Some people may have high blood pressure.
An infant who has polycythemia may be feeding poorly and have low blood sugar and difficulty breathing. It's very important to note that the problem isn't a cause for major concern in babies. It often doesn't require treatment, and it often resolves within a few days. However, these symptoms do warrant a visit to the doctor. Only very rarely does polycythemia cause serious problems in babies, such as seizures due to poor circulation to the brain.
Anyone who has polycythemia vera must receive treatment. Without treatment, the symptoms will become much worse and the risk of death from stroke, blood clots, or heart attack will increase. With proper treatment, the average survival of people with polycythemia vera is 7 to 15 years. People will probably feel quite normal and their risk of stroke or heart attack will be much less than if they didn't seek treatment. Although there's no cure, most people live for more than 10 years with the disease. Blood clots are the most common cause of death, followed by complications of myeloid metaplasia (a progressive disease of the bone marrow), hemorrhage, and development of acute leukemia.
Making the Diagnosis
To diagnose polycythemia, a doctor will begin by discussing the patient's health history and doing a physical examination. The doctor will check for evidence of low brain or lung blood flow by asking about symptoms such as headache, weakness, tinnitus (ringing or buzzing in the ears), or vision problems. The doctor will also look for physical signs of increased blood volume, such as dilated veins and a ruddy complexion. If the skin is flushed or itchy, particularly after a hot bath, it may indicate a diagnosis of polycythemia.
The doctor may also check for a history of smoking or alcohol abuse or a family history of kidney disease. A careful physical examination might also be done to check for high blood pressure, obesity, lack of oxygen (cyanosis), heart murmurs, or abdominal noises (audible swishing or murmuring sounds heard over an artery or vascular channel, called bruits). Various blood tests will likely be done, including a complete blood cell count and measurement of levels of vitamin B12 and certain other substances. Uric acid levels may also be increased and should be checked. Your doctor may also order tests for gene mutations associated with the condition.
Additional tests will then be done to find out whether it is polycythemia vera or secondary polycythemia. These tests will probably include a history and physical examination, measurements of oxygen saturation, and a complete blood count. For some people, the doctor may suggest a bone marrow test. A blood test to look for a mutation in a protein called Jak-2 may be performed.
Treatment and Prevention
Treatment will vary according to the person's age, gender, medical status, symptoms, and blood test results.
To reduce the risk of blood clots, treatment with low-dose acetylsalicylic acid* (ASA) is recommended for most people with polycythemia (unless there is a reason they should not take it).
Phlebotomy (removal of small amounts of blood) used to be the most common type of therapy for polycythemia vera.
When phlebotomy is used, blood will be withdrawn in amounts of 300 mL to 500 mL every few days at first, then every few weeks, and then every few months. The treatment goal will be to keep the blood hemoglobin level within the low-to-normal range. Often, the process of blood withdrawal can be stopped for months at a time if the hemoglobin level stays in the required range. For seniors or for people with heart or brain blood vessel disease, less blood is usually taken (i.e., only 200 mL to 300 mL twice a week). Once a person's hemoglobin levels are normal, he or she will probably have monthly doctor's appointments.
If the blood has high white blood cell and platelet counts in addition to a high content of red blood cells, the physician may prescribe a medication that cuts down blood cell production by the bone marrow (e.g., radioactive phosphorus). This medication has a success rate of 80% to 90%. Remissions may last from 6 months to several years. This medication has few side effects. Its main advantage is that people need fewer follow-up visits when the disease is controlled. In fact, just one treatment a year may be enough to control the disease. A disadvantage of radioactive phosphorus therapy is that it may turn normal white cells into leukemia cells. For this reason, it is rarely used.
Other medications may be used on a daily basis to lower both the white blood cell count and the platelet count. For example, hydroxyurea is commonly used.
Complications such as high uric acid blood levels and itchy skin may be treated with allopurinol or antihistamines, respectively.
In rare cases, the spleen can become extremely enlarged. The physician may recommend its surgical removal (splenectomy). Anyone who has had a splenectomy must get vaccinations to prevent future infections.
If the disorder seems to be causing considerable problems in an infant, up to several ounces of blood can be removed and replaced with intravenous fluid. This procedure usually dilutes the circulating red blood cells until they return to a normal level.
Unfortunately, there's no way to prevent polycythemia vera. However, you may reduce your risk of secondary polycythemia by not smoking and by not spending long periods of time at high altitudes.
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.