Polycythemia
(Polycythemia Vera · Primary Polycythemia · Secondary Polycythemia)
In this condition factsheet:
The Facts on Polycythemia
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.
Causes of Polycythemia
Polycythemia vera is a primary bone marrow disorder. Bone marrow is found in the centre of most bones and normally produces all red blood cells and platelets, and most white blood cells. In polycythemia vera, a mutation occurs in a bone marrow cell, resulting in overproduction of the bone marrow cells. The overproduced cells include the red blood cells, but can also include white blood cells and platelets. Although the exact cause of polycythemia vera is unknown, researchers have found that a specific gene mutation in the JAK2 gene is present in over 90% of cases. Polycythemia vera is an uncommon condition It occurs more often in men than in women. It is rarely seen in people under the age of 40.
Secondary polycythemia is different from polycythemia vera in several ways. Secondary polycythemia occurs when the body is not getting enough oxygen or as a response to certain drugs or hormones. Red blood cell production increases 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.
Symptoms and Complications of Polycythemia
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. Polycythemia is associated with an increased risk of blood clots (venous thrombosis, stroke, heart attack) and leukemia.
Without treatment, the risk of death from stroke, blood clots, or heart attack increases. Blood clots are the most common cause of death, followed by complications of myelofibosis (a condition in which the bone marrow is replaced by scar tissue), hemorrhage, and development of acute leukemia.
