Only five people out of every million have this rare condition. The average age at which the disorder is diagnosed is 60 years, but it can develop at an earlier age. The excessive numbers of red blood cells produced in polycythemia increases the volume of blood and makes it thicker so that it flows less easily through small blood vessels. However, the number of red blood cells may be increased for a long time before symptoms appear. The earliest symptoms frequently include weakness, fatigue, headache, light-headedness and shortness of breath. Vision may be distorted and a person may have blind spots or may see flashes of light. Bleeding from the gums and from small cuts is common, and the skin - especially the face - may look red. A person may itch all over, particularly after a hot bath. Burning sensations in the hands and feet or, more rarely, bone pain may be felt. As the disorder progresses, the liver and spleen may enlarge, causing a dull, intermittent ache in the abdomen.

The excess of red blood cells may be associated with other complications, including stomach ulcers, kidney stones or clotting in veins and arteries, which can cause heart attacks or strokes and can block blood flow to the arms and legs. Rarely, polycythemia vera progresses to leukemia; certain treatments increase this likelihood.

Hemoglobin levels and hematocrit are abnormally high when this condition is present. A hematocrit reading higher than 54% in a man or 49% in a woman may indicate polycythemia, but the diagnosis can not be made on the basis of this alone. A test that uses radioactively-labeled red blood cells to determine the total number of red blood cells in the body can help make the diagnosis. Rarely, a bone marrow biopsy is needed.

Prognosis and Treatment
Without treatment, about half the people who have polycythemia vera with symptoms die in under 2 years. With treatment, they live for an average of 15 to 20 years.

The aim of treatment is to slow down production and decrease the number of red blood cells. Blood is usually removed from the body in a procedure called a phlebotomy: a pint of blood is removed every other day until the hematocrit begins to decrease. When the hematocrit reaches a normal level, blood is removed every few months, as needed.

To help control some of the symptoms, antihistamines can help relieve itching, and aspirin can relieve burning sensations in the hands and feet as well as bone pain.