Polycythemia Rubra Vera, also known as PRV, is the primary presentation of the disease polycythemia. This rare condition occurs when the bone marrow produces an excessive number of red blood cells, making the blood thicker. This condition can often be traced back to a single stem cell in the marrow that suddenly becomes overproductive. PRV is most often seen in white males over 50.
The cause for PRV is still unknown, although the condition does not appear to be heritable or infectious. Current research indicates that some PRV sufferers may carry a mutation in the cell receptor that binds a cytokine called erythropoietin. This cytokine is required for erythropoiesis, the process that creates red blood cells. The mutation prevents any regulation of cytokine binding; hence it overstimulates erythropoiesis and creates too many red blood cells. Another possible cause of PRV is the gene product called PRV-1, which is another receptor that is overexpressed in patients. Additional research is required to pinpoint the true cause of PRV in order to better treat the condition.
Many people with PRV have minor or no symptoms, and the severity and progression of the disease also varies greatly between patients. Most symptoms that develop are because of a decrease in blood flow due to the increased number of cells. This decreased flow can cause engorgement of blood vessels, causing a reddish complexion in the hands, feet and regions of the face including lips, cheeks, ears, and nose. This reddened complexion, also called plethora, is a hallmark sign of PRV. The decreased blood flow can also affect the brain, causing headaches, dizziness, and blurred vision. For unknown reasons PRV sufferers often have itchy skin that is especially pronounced after taking hot showers or baths. The patient may also bruise or bleed easily and a small percentage also develops gout.
While the symptoms of PRV appear to be relatively minor, the disease can develop severe, life-threatening complications. The thickened blood increases the risk of blood clots, also called thrombosis, which can cause strokes. Additionally, a small percentage of PRV patients will also develop leukemia. It is therefore important to treat and monitor the disease to lessen these risks.
There is no cure for PRV, however there are several long-term treatments that can control the number of red blood cells. The traditional treatment is bloodletting, also called venesection, that is performed roughly every couple of weeks. This treatment is very effective at reducing red blood cell counts, although it can lead to iron deficiency (anemia) if performed too often. An alternative treatment is drugs that are normally used for chemotherapy, such as hydroxyurea. These drugs target and suppress the activity of the bone marrow, lowering the amount of red blood cells. However, like other chemotherapeutics, these drugs produce may unpleasant side effects, including nausea and weight loss. A third treatment is phosphorus-32, a radioactive isotope that also inhibits the marrow’s production of red blood cells. This treatment appears to be successful in most patients and one injection can be effective for about a year. Side effects from 32P appear minimal since the amount of radioactivity used in this treatment is very minor.