Overview Of Polycythemia Vera Biology Essay

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Polycythemia Vera ("PV") is an atypical blood disorder that is caused by the overproduction of red blood cells. It is classified as a Myeloproliferative Disorder, which is included in a classification of slow-growing cancers of the blood. "Myeloproliferative Disorders primarily affect red blood cell production, although white blood cells and platelets can also be affected by this condition, which results in an elevated production of abnormal cells in the bone marrow and peripheral blood." (National Cancer Institute) PV is slow to develop, and often goes undetected until blood tests, such as a Complete Blood Count (CBC) are conducted for some other reason.

Blood cells are manufactured in the bone marrow in bones. Red blood cells, or erythrocytes, deliver oxygen to organs throughout the body, and remove carbon dioxide from them as blood travels through blood vessels. White blood cells, or leukocytes, aid in infection control, and platelets help blood to clot. Uncontrolled production of erythrocytes, as seen in PV, causes the blood to be thicker, altering the viscosity level of the blood. This thicker viscosity produces a slower flow of blood through the blood vessels, and a reduced amount of oxygen being delivered to vital organs. The increased amount of blood cells can result in an enlarged spleen as the numerous blood cells become trapped there, and the incidence of clots in blood vessels can also be increased.

PV, or Primary Polycythemia, is mainly caused by a mutation of the Janus kinase 2 (JAK2) gene. The normal function of this gene is to aid in the production of specific proteins essential for the growth and development of cells. Control of the JAK2 protein is especially significant in developing stem cells in the bone marrow which can grow into erythrocytes, leukocytes and platelets. A change, or mutation, in this gene is an acquired, or somatic mutation, and is not inherited, and its cause is unknown. "The most common mutation (the V617F mutation) replaces the protein building block (amino acid) valine with the amino acid phenylalanine at position 617 in the protein. This particular mutation is found in approximately 96 percent of people with polycythemia vera." (Genetics for Home Reference, 2011) In essence, when this mutation is present, the protein is always activated, and the production of blood cells increases.

Secondary Polycythemia is not gene-linked, but rather results from an overproduction of the hormone erythropoietin (EPO). Increased EPO can contribute to the overproduction of red blood cells, resulting in Secondary Polycythemia. Conversely, a significantly low level of EPO can signal Primary Polycythemia. Physiologic Polycythemia is a type of Secondary Polycythemia, and is related to long-term exposure to low oxygen levels, and is seen in people who are at often at high altitudes, and those who smoke or have lung or heart disease.

Symptoms of this slow developing condition include: breathing difficulty when lying down, dizziness, fullness in the left upper abdomen (due to enlarged spleen), headache, itchiness (especially after a warm bath), red coloring of the face, shortness of breath, symptoms of phlebitis, bluish skin discoloration, fatigue, red skin spots and vision problems. (Medline Plus, 2011) Symptoms often do not present for years after contracting this condition, and are result of the thickness of the blood due to the increased number of red blood cells. Typically, only five new cases of polycythemia vera are diagnosed each year for every one million people. It is rarely seen in individuals under the age of 20, and most often occurs in people over 60, affecting more men than women.

Several blood tests can be used to diagnose PV. The primary test used to determine PV is a CBC, which measures many key blood components, including hemoglobin, which carries oxygen, and hematocrit, which is a measure of the percentage of packed red blood cells in the blood. A blood smear is a microscopic examination of blood to determine the amount of red blood cells and any abnormalities in those cells which can lead to myelofibrosis. EPO levels are determined through an erythropoietin level test, and are indicators of PV, with low levels indicating Primary Polycythemia, and higher levels pointing to Secondary Polycythemia. Testing of bone marrow to determine the amount of blood cells being produced is another method of testing for PV. Bone marrow test consist of aspiration and biopsy. "Bone marrow aspiration usually is done first, and a small amount of fluid bone marrow is removed through a needle for examination. A bone marrow biopsy is a follow-up test, and it also involves removing bone marrow through a needle. It is done when an aspiration doesn't give needed information, or if examine of the bone marrow structure itself is required." (National Heart Lung and Blood Institute, 2009)

The sluggish blood flow associated with PV is a major factor contributing to serious health complications. Blood clots can easily form and cause a heart attack or stroke, and can also be due to abnormal platelets levels associated with PV. "Blood clots occur in about 30 percent of patients before the diagnosis of PV is made. During the first 10 years after diagnosis, 40 to 60 percent of PV patients may have blood clots." (Leukemia and Lymphoma Society, 2007) An enlarged liver, in addition to the aforementioned enlarged spleen can also occur. These filtering organs are affected because they are forced to work harder and are often overloaded by the thick blood. Decreased oxygen flow to vital organs can result in angina or heart failure, and the excessive amounts of red blood cells can lead to gout, kidney stones and ulcers. Myelofibrosis develops in rare instances, and is a condition that results when bone marrow is replaced with scar tissue. Other rarities include the failure of stem cells to properly mature or function termed myelodysplastic syndrome, and acute leukemia, or cancer of the blood and bone marrow.

Although there is no cure for chronic PV, long-term management of the condition is usually met with success. Treatment includes focus on maintaining near-normal levels of hemoglobin, hematocrit and platelets, and is routinely accomplished through phlebotomy and drug therapy. Phlebotomy used in treatment of PV involves the removal of blood from a vein, and is no different from a standard blood donation. When used as a treatment option for PV, blood is withdrawn at intervals determined by a physician, significantly reducing hemoglobin and hematocrit levels and blood volume. Platelet levels usually increase with such blood draws, and those levels must be carefully monitored during treatment to avoid possible clotting.

Drug therapy is used when phlebotomy alone is not sufficient in treating PV. "Medications, such as hydroxyurea or anagrelide, which suppress the bone marrow's ability to produce blood cells, and radioactive phosphorus (phosphorus 32 or p-32) also can be used to reduce the number of red blood cells. Interferon-alpha may be used to stimulate the immune system to fight the overproduction of red blood cells." (Mayo Clinic, 2009) Finally, low-dose aspirin is used to inhibit clot production, and antihistamines can relieve the itch commonly associated with PV.

Individuals who are diagnosed with Polycythemia vera can contribute to treatment success with moderate physical activity. Activities that increase the heart rate lead to increased blood flow, which reduces the possibility of clots. Additional natural therapies for reducing blood clots or platelet levels are grape juice, kiwi, green tea, vitamin E and dark chocolate. As with any condition follow-up care with a physician, is essential to monitoring the condition.