Polycythemia vera

Polycythemia vera is a condition where the bone marrow, due to changes over time rather than any external stimulus, starts overproducing red blood cells. The cells start to make the blood more viscous, resulting in it being harder for it to travel through the body. In most cases, there is also an overproduction of white blood cells and platelets. Although it can affect anyone, it tends to be more common as people age, and is more common in men than in women. It can be the result of toxic exposure.
Polycythemia vera can be asymptomatic and have symptoms come on very suddenly. Since the thicker blood is more prone to clots, often the first indication that a patient has the condition is a heart attack. It can also present with erythromelalgia - a sudden intense burning sensation in the hands or feet, often with the skin turning red or blue in color.
However, in most cases, the symptoms are more prosaic, making the condition a zebra diagnosis. For example, the most common symptom is itching, which usually occurs when a patient's skin is soaked in warm water. The condition can easily be mistaken for gout in some cases. Peptic ulcers are also associated with the condition, although the reason for this is not clear.
Diagnosis of the condition requires a lengthy differential. Patients usually present with an enlarged liver or spleen, both of which process the by-products of dead red cells. Blood tests will show hemoglobin and hematocrit levels almost double the normal range. Conversely, erythropoietin levels will be lower than normal.
The condition is incurable and can be fatal without treatment. Bloodletting is often used to reduce red blood cell levels. Low dose aspirin helps prevent clots. In severe cases, chemotherapy can be used, but it can often lead to a form of leukemia in younger patients.
Polycythemia vera at NIH
Polycythemia vera at Wikipedia
Polycythemia vera at Mayo Clinic
Polycythemia vera