Polycythemia Vera (PCV)
In polycythemia vera (PCV), the body makes too many red blood cells, leading to a thickening of the blood. It can be associated with an elevated platelet count and an enlarged spleen.
This slow-developing disease is linked to a mutation in the gene JAK2, which regulates the production of blood cells. This is an acquired disease, not an inherited genetic problem, occurring later in life.
PCV is both chronic and progressive. No one knows its cause.
Patients may not have any symptoms or they may have the kind of complaints that are discovered during a routine physical exam, including:
- Sweating during the day or night
- Ringing in the ears
- Blurred vision or blind spots
- Reddish or purplish skin
- Unexpected weight loss
- Problems with bleeding or clotting
- A perennial feeling of fullness
- Itching, especially after taking a shower
- Burning and redness of the hands or feet
- Bone pain
In many cases, a routine complete blood count reveals an increase in the red blood cells along with an increase in the white blood cells or platelets. A physician may also recognize certain signs of this disease during an ordinary office visit, including a redness of the complexion or an increase in the size of the spleen.
Common diagnostic tests include:
- Complete blood count to check for an increase in the hemoglobin (along with the white blood cells or platelets)
- Genetic testing for the JAK2 mutation (positive in 95% of PCV patients)
- Further blood tests to look for a low erythropoietin level (a hormone involved in red blood cell production)
- Bone marrow biopsy to look for proliferation of precursors to red blood platelets, red blood cells, and white blood cells
- Gender. Men are slightly more likely than women to develop the condition.
- Age. Though PCV can be diagnosed at any age, it is most commonly found in patients over 60.
- Exposure to intense radiation. This may also increase the risk for PCV.
- Environmental toxins. There is speculation that PCV may be triggered by exposure to toxic substances, but there have been no definitive studies in this area. A cluster of PCV cases has been reported in three counties in Pennsylvania adjacent to a Superfund Cleanup site and is under study now.
- Gene mutations. Ninety-five percent of patients with PCV have a mutation in the JAK2 gene. The discovery of this mutation has inspired research that will hopefully lead to new and effective treatments.
For most patients, this disease is chronic. That means they tend to live longer than other patients with myeloproflierative neoplasms (MPN) but have to deal with ongoing symptoms, including itching after bathing, general fatigue, or blood clotting. Complications of this disease may include cardiovascular events such as a stroke, mini-stroke, or heart attack or problems in the veins, including deep vein thrombosis, pulmonary embolus, and blood clots.
Roughly 15% of patients suffer from myelofibrosis, a progressive bone marrow disorder that results in bone marrow scarring, severe anemia, and enlargement of the liver and spleen. In a few cases, PCV may progress to acute leukemia (AML).
The progression of this disease varies with each patient, as does the treatment. Getting the hematocrit (HCT), a measure of the red blood count, to less than 45 has been shown to improve survival and is the goal of treatment.
Treatment options may include:
- Phlebotomy—Removal of blood to reduce the overall number of blood cells. With fewer cells, the blood “thins” and flows more easily and symptoms generally improve.
- Low-dose aspirin—Aspirin keeps platelets from sticking together and can prevent life-threatening blood clots causing heart attacks and strokes.
- Hydroxyurea—a drug that can help to control the HCT in patients when phlebotomy does not work completely.
- Pegylated interferon—a therapy that alters the growth and survival of the abnormal polycythemia cells.
- Ruxolitinib (Jakafi)—a drug that targets the JAK2 protein. This drug was approved by the FDA for patients who no longer respond to hydroxyurea or have too many side effects from hydroxyurea.