Polycythemia vera (PV) is an extremely rare blood disorder (five cases per million persons) which causes the red blood count to be much higher than normal. For persons with PV, the production of red blood cells goes into overdrive causing the body to produce more red blood cells than is healthy for the average person.
The affect of the presence of these extra red blood cells is that the blood actually thickens, causing it to flow more slowly. As a result of the slower blood flow, you may be more prone to experience blood clots or blocked arteries and veins. This disorder may also lead to angina, heart failure or heart attack and stroke.
PV has also been known to lead to the enlargement of the liver and spleen, stomach ulcers, kidney stones, gout, myelofibrosis (bone marrow replaced by scar tissue) and acute myelogenous leukemia (AML).
PV is a slow acting disease and a person may have undiagnosed PV for years before symptoms present themselves. According to the National Heart Lung and Blood Institute, when symptoms do present themselves, they include: “headaches, dizziness, itching, and vision problems such as blurred or double vision.” In addition, persons may experience unusual bleeding around the gums or from small cuts. Fatigue, weight loss and difficulty breathing or shortness of breath may also be symptoms of PV. There is also a tendency for the spleen to enlarge so persons with PV may also experience “feelings of pressure or fullness on the left side of the abdomen.” (NHLBI)
Types of polycythemia:
There are two main types of PV, polycythemia vera (primary polycythemia) and secondary polycythemia. Each of these two types of polycythemia are caused by different stimuli.
Primary polycythemia is caused by a mutation in the JAK2 gene (the JAK2 V617F mutation). More than 90% of persons with PV possess the JAK2 gene mutation. The JAK2 gene supplies the body with a special protein that actually tells the red blood cells to grow. When the JAK2 gene mutates, the red blood cells grow –- and grow –- and grow. The cause of the JAK2 gene mutation isn’t known.
Primary polycythemia tends to run in families.