 |
|
| ||||||||||||||||||||||||||
|
|
| ||||||||||||||||||||||||||
|
|
|
|
|
| ||||||||
Polycythemia is a condition in which there is a net increase in the total circulating erythrocyte (red blood cell) mass of the body. There are several types of polycythemia.
Primary polycythemia, often called polycythemia vera (PCV), polycythemia rubra vera (PRV), erythremia, or just PV, occurs when excess erythrocytes are produced as a result of tumorous abnormalities of the bone marrow. Often, excess white blood cells (leukocytosis) and platelets (thrombocytosis) are also produced. It is, therefore, classified as a myeloproliferative disease.
In primary polycythemia there may be 8 to 9 million and occasionally 11 million erythrocytes per cubic millimeter of blood, and the hematocrit may be as high as 70 to 80%. In addition, the total blood volume sometimes increases to as much as twice normal. The entire vascular system can become markedly engorged with blood, and circulation times for blood throughout the body can increase up to twice the normal value. The increased numbers of erythrocytes can increase the viscosity of the blood to as much as five times normal. Capillaries can become plugged by the very viscous blood, and the flow of blood through the vessels tends to be extremely sluggish.
As a consequence of the above, people with untreated PV are at a risk of various thrombotic events (deep venous thrombosis, pulmonary embolism), heart attack and stroke, and have a substantial risk of Budd-Chiari syndrome (hepatic vein thrombosis). The condition is considered chronic; no cure exists. Symptomatic treatment (see below) can normalize the blood count and most patients can live a normal life for years.
Secondary polycythemia is caused by either appropriate or inappropriate increases in the production of erythropoietin that result in an increased production of erythrocytes. In secondary polycythemia their may be 6 to 8 million and occasionally 9 million erythrocytes per cubic millimeter of blood. A type of secondary polycythemia in which the production of erythropoietin increases appropriately is called physiologic polycythemia. Physiologic polycythemia occurs in individuals living at high altitudes (4275 to 5200 meters), where oxygen availability is less than at sea level. Such people may have 6 to 8 million erythrocytes per cubic millimeter of blood.
Other causes of secondary polycythemia include smoking, renal or liver tumors, or heart faults that result in hypoxia.
Relative polycythemia is an appearent raise of the erythrocyte level in the blood; however, the underlying cause is reduced plasma blood. Relative polycythemia is often caused by low fluid intake or stress.
As the condition cannot be cured, treatment focuses on reducing the erythrocyte levels.
Blood letting is one form of treatment, which often may be combined with other therapies. The removal of blood from the body reduces the blood volume and brings down the hematocrit levels.
Chemotherapy for polycythemia may used sparingly, when the rate of bloodlettings required to maintain normal hematocrit is not acceptable. This is usually with a "cytoreductive agent" (hydroxycarbamide/hydroxyurea).
The tendency to avoid Chemotherapy if possible, especially in young patients, is due to research indicating increased risk of transformation to AML, and while hydroxycarbamide/hydroxyurea is considered safer in this aspect, there is still some debate about its long range safety.
Other therapies include Interferon, and in cases where secondary trombocytosis is present, anagrelide may be prescribed.
Bone marrow transplants are rarely undertaken in polycythemia patients.
| Lymphoma (Hodgkin's disease, NHL) - Leukemia (ALL, AML, CLL, CML) - Multiple myeloma - MDS - Myelofibrosis - Myeloproliferative disease (Thrombocytosis, Polycythemia) - Neutropenia |
| Anemia - Hemochromatosis - Sickle-cell anemia - Thalassemia - other hemoglobinopathies |
|
Coagulation and Platelets |
| Thrombosis - Deep venous thrombosis - Pulmonary embolism - Hemophilia - ITP - TTP |
|
||||
| View Live Article | This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License | |
||
