Polycythemia is a condition in which the volume of red blood cells in the blood is abnormally high. It may be due to excess red blood cells, in which case it is known as absolute polycythemia, or to a decreased blood plasma volume, a condition called relative polycythemia. Absolute polycythemia may be further classified as primary, secondary, or Chuvash polycythemia. Polycythemia symptoms vary depending upon the cause of the condition.
In primary polycythemia, also called polycythemia vera, the bone marrow overproduces red blood cells. It may also produce too many white blood cells and platelets. Primary polycythemia symptoms, when they occur, include itching, especially after exposure to warm water, joint pain, headache, fatigue, and an inability to concentrate. Less common symptoms are thrombosis or blood clots, gouty arthritis, ulcers in the gastrointestinal tract, and erythromelalgia, in which excess platelets cause burning and skin discoloration in the hands and feet. However, polycythemia vera is often asymptomatic.
Secondary polycythemia is caused by excess production of erythropoietin, the hormone that controls red blood cell production. Secondary polycythemia can be a complication of hypoxic disease, in which oxygen levels in the blood are low, or of genetic mutations or kidney or liver tumors. It can also result from bloodletting or from high altitudes.
Secondary polycythemia symptoms caused by high altitudes include nausea, vomiting, and lack of appetite, fatigue, dizziness, insomnia or drowsiness, a tingling sensation, shortness of breath, nosebleed, rapid pulse, and edema or swelling of the hands and feet. In more severe cases, edema can affect the lungs or brain. When associated with low oxygen levels caused by lung disease, secondary polycythemia symptoms include sleep apnea and chronic cough. Polycythemia induced by cancer of the liver or kidney may present with weight loss, abdominal pain, or jaundice, a yellow discoloration of the skin and eyes.
Chuvash polycythemia is a hereditary form of the disorder. It can cause blood clots and other cardiovascular disturbances, especially later in life. Other symptoms are similar to those of polycythemia vera.
Relative polycythemia is often caused by a loss of bodily fluids through dehydration, burns, or stress. However, it can also be caused by apparent polycythemia, a condition associated with cigarette smoking, excess alcohol consumption, and high blood pressure. A common symptom of relative polycythemia is high blood pressure, and symptoms similar to those of polycythemia vera may also be present.