Polycythemia Vera (PV) is a rare condition where the bone marrow makes too many red blood cells (RBCs). The affected individual has increased number of white blood cell (WBC) and platelets also.
Excess amount of RBC in the blood makes the blood thicker than normal. Thicker blood flows slowly in the blood vessels, thereby depriving all part of the body from getting enough oxygen.
Lack of oxygen can result in complications like chest pain and heart failure. Thicker blood also forms clot more easily and blocks the arteries and veins, which ultimately results in heart attack and stroke.
The important function of RBC is to deliver oxygen to all parts of the body and remove carbon dioxide from every cell so that it is exhaled out. PV is a serious ongoing disease that requires continuous monitoring; if the disease is not diagnosed and treated it can be fatal.
PV cannot be cured but the symptoms can be controlled. PV occurs more often in people who are above 60 years of age.
Polycythemia is of two types.
What causes PV is not fully understood. But all patients with PV carry a mutation (change in the genetic material, DNA) in the JAK2 gene (Janus kinase 2 gene, which gives instruction in making protein that promotes growth and cell division). This mutation is likely to play a major role in the onset of PV. But what initiates the disorder and what causes change in the JAK2 gene is still unclear.
PV is not transferred from parents to children. However, occasionally more than one family member may suffer from PV.
Another type of PV called as secondary PV, which is in no way related to JAK2 mutation, is caused due to long term exposure to low oxygen environment like being in high altitudes, smoking, and severe lung or heart disease.
The symptoms of PV develop slowly, and initially it does not show any symptoms. When symptoms do show, they are due to thick blood that prevents easy blood flow to all parts of the body and deprives organs from sufficient oxygen-rich blood. Without oxygen many organs do not function normally. PV can cause symptoms like:
As PV does not cause any signs and symptoms, it is diagnosed accidentally during blood test done for other purpose.
PV is suspected based on the patient’s age, medical history, family history, physical examination, overall health, and few tests.
During physical examination doctor might look for enlarged spleen, redness in the face, and bleeding from gums.
If PV is confirmed, then the next step is to find out whether it’s primary or secondary PV.
Differentiation is done by simple physical examination and medical history, if they do not provide conclusive results then the level of erythropoietin (EPO) hormone is checked.
Complete blood count (CBC) is done to measures the level of hemoglobin and hematocrit (volume of RBC in blood). High level of both suggests PV.
CBC can also provide information about the number of RBC, WBC, and platelets.
A blood smear is a microscopical study of the blood cells, which shows the number of blood cells, any abnormality in the structure of blood cells. Abnormal type of blood cells are linked to myelofibrosis, a condition related to PV.
Erythropoietin level (EPO) is a hormone that stimulates bone marrow to make blood cells, measuring the level of EPO is an essential diagnostic procedure for PV.
A decreased level of EPO confirms primary PV; secondary PV has normal or increased level of EPO. Bone marrow test shows whether the bone marrow is healthy and whether it’s making normal amount of blood cells. Too many blood cells by the bone marrow confirms PV.
Genetic test that looks for the presence of JAK2 mutation is done. Elevated level of WBC and platelets are seen in 50% of the patients.
Treatment for PV is aimed at reducing the thickness of blood and preventing bleeding and clotting. Phlebotomy is one of the treatment options. During this procedure, a needle is inserted into the vein and some amount of blood is removed from the body into a sterile bag. This is done weekly and every time a pint (1 unit) of blood is removed until the hematocrit value is less than 45.
Drugs like hydroxyurea and interferon-alpha are prescribed, which keeps the bone marrow from making too many blood cells.
Hydroxyurea is a cancer drug that reduces the number of RBC and platelets and brings down the thickness of blood close to normal.
Interferon-alpha triggers the immune system to fight against the bone marrow that is making too many blood cells.
Radiations usually suppress the overactive bone marrow and reduce the number of blood cells.
Preventing primary PV is impossible, however, symptoms and complications can be prevented by taking proper treatment. Secondary PV can be prevented to an extent by avoiding all situations that deprives body of oxygen for long period.