What is polycythemia?

 Polycythemia is a condition that results in an increased level of circulating red blood cells in the bloodstream. People with polycythemia have an increase in hematocrit, hemoglobin, or red blood cell count above the normal limits. Polycythemia is normally reported in terms of increased hematocrit or hemoglobin.

 Hematocrit (HCT): Polycythemia is considered when the hematocrit is greater than 48% in women and 52% in men.

 Hemoglobin (HGB): Polycythemia is considered when a hemoglobin level of greater than 16.5g/dL in women or hemoglobin level greater than18.5 g/dL in men.

 Polycythemia can be divided into two categories; primary and secondary

Primary polycythemia: In primary polycythemia the increase in red blood cells is due to inherent problems in the process of red blood cell production

 Secondary polycythemia: Secondary polycythemia generally occurs as a response to other factors or underlying conditions that promote red blood cell production.

 What causes polycythemia?

Causes of polycythemia are primary or secondary. In primary polycythemia, intrinsic factors in red blood cell production cause an increase in red cell count. In secondary polycythemia, external factors result in polycythemia.

What are the causes of primary polycythemia?

Primary polycythemias are due to acquired or inherited genetic mutations causing abnormally high levels of red blood cell precursors. Primary familial and congenital polycythemia (PFCP) and polycythemia vera (PV) are in this category.

 Polycythemia vera

 Polycythemia vera is a rare condition occurring only in about one person per one million in the United States. Polycythemia vera is typically associated with an elevated white blood cell count (leukocytosis) and platelet count (thrombocytosis). An enlarged spleen (splenomegaly) and low erythropoietin levels are other clinical features of polycythemia vera. Until recently, the exact mechanism of polycythemia vera was not well understood. In 2005, genetic mutations of the JAK2 gene were found to be responsible for most cases of polycythemia vera. These mutations are thought to possibly increase the sensitivity of the red blood cell precursors to erythropoietin, thereby, increasing red blood cell production.

Primary familial and congenital polycythemia (PFCP)

 Primary familial and congenital polycythemia (PFCP) is also thought to be caused by genetic mutations resulting in increased responsiveness to normal levels of erythropoietin. Most cases are caused by different mutations to the EPOR gene

 What are the common causes of secondary polycythemia?

 Secondary polycythemia is usually due to increased erythropoietin (EPO) production either in response to chronic hypoxia (low blood oxygen level) or from an erythropoietin secreting tumor.

 Chronic hypoxia Common conditions causing chronic hypoxia are chronic lung diseases such as: emphysema and chronic bronchitis which are collectively known as chronic obstructive pulmonary disease (COPD) or hypoventilation syndrome, chronic heart diseases (congestive heart failure, or abnormal flow of blood from the right side to the left side of the heart), sleep apnea, and pulmonary hypertension. Abnormal blood flow to the kidneys can be perceived by the kidneys as decreased oxygenation (renal hypoxia), even though, other tissues may have normal oxygenation. Renal hypoxia may promote an increase in erythropoietin production. This condition can occur after kidney transplantation or narrowing of renal arteries (blood vessels supplying the kidneys). People living in high altitudes can develop polycythemia. In high altitudes, increased red blood cell production occurs in order to compensate for the low ambient oxygen levels and inadequate tissue oxygenation. Rare congenital defects in the hemoglobin molecule, such as 2, 3-BPG deficiency, can result in a higher oxygen affinity by hemoglobin. In these conditions, oxygen is held on tightly by hemoglobin and is less readily released from hemoglobin to the tissues. The resulting tissue hypoxia from poor oxygen delivery may lead to polycythemia.

 Erythropoietin secreting tumors Certain tumors can release increased amount of erythropoietin. The most common erythropoietin secreting tumors are: liver cancer (hepatocellular carcinoma), kidney cancer (renal cell carcinoma), adrenal adenoma (adenocarcinomas), and uterine (womb) tumors. Occasionally, benign kidney cysts and kidney obstruction (hydronephrosis) can also secrete extra erythropoietin causing polycythemia. A rare genetic condition, called Chuvash polycythemia, causes increased activity of the gene that produces erythropoietin. The overproduction of erythropoietin causes polycythemia.

What are the risk factors for polycythemia?

 Hypoxia from long standing (chronic) lung disease and smoking are common causes of polycythemia. Therefore, smoking can be significant risk factor for polycythemia. Chronic carbon monoxide (CO) exposure can also be risk factor for polycythemia. Hemoglobin has a higher affinity for CO than for oxygen; therefore, as it replaces oxygen in favor of CO, polycythemia may ensue to compensate for the low oxygen carried by hemoglobin. Chronic carbon monoxide exposure is a risk factor for people working in underground tunnels or parking garages, cab drivers in highly polluted and congested cities, or workers in factories with exposure to engine exhaust. People living at high altitudes may also be at risk of developing polycythemia due to low environmental oxygen levels. People with genetic mutations and familial types of polycythemia and certain hemoglobin abnormalities also carry risk factors for this condition as mentioned in earlier sections.

 What are the symptoms of polycythemia?

 Symptoms of polycythemia can be none to minimal in many people. There are some general and non-specific symptoms that can be seen with polycythemia. Some of these include: weakness, fatigue, headache, itching, bruising, joint pain, dizziness, or abdominal pain. In patients with polycythemia vera, other blood disorders are also very common. Thus, bleeding problems or clotting events may be seen in these patients. Itching after showers or baths (post-bath pruritus) can also be seen in patients with polycythemia vera for unclear reasons. Joint pains also common in patients with polycythemia vera. Symptoms of secondary polycythemia may be more closely attributed to the underlying condition, such as, chronic lung disease, than to polycythemia itself. Therefore, shortness of breath, chronic cough, sleep disturbance (sleep apnea), dizziness, poor exercise tolerance, or fatigue may be common in patients with polycythemia. If polycythemia is related to kidney cancer, liver cancer, or other erythropoietin secreting tumors, the symptoms of these conditions, such as, weight loss, abdominal pain or fullness, or jaundice may be predominant.

What is the treatment for polycythemia?

 The treatment for polycythemia is generally dependent on the cause. In polycythemia vera or other primary polycythemia syndromes, the treatment options are more specific. Phlebotomy (drawing blood or blood letting) is the most essential part of the treatment. The recommended hematocrit of less than 45 in men and less than 42 in women is the goal of phlebotomy. Several medications have been considered in conjunction with phlebotomy to suppress the abnormal production of red blood cells. Most of these chemotherapeutic drugs have been linked with side effects and their use has been controversial and limited. The medication hydroxyurea (Hydrea) has been recommended for some patients with primary polycythemia and higher risk of blood clot formation due to high blood viscosity. The factors favoring treatment with hydroxyurea are age greater than 70, platelet count greater than 1.5 million, and general cardiovascular risk factors. Aspirin and other anti-platelet agents (dipyridamole) may also be beneficial in patients with polycythemia by reducing clotting complications, unless the patient has a history of bleeding problems. In patients with secondary polycythemia, the goal is to treat the underlying condition. For example, in patients with lung or heart disease with hypoxia, appropriate management of these conditions along with oxygen supplementation is generally advised.

 What are the complications of polycythemia?

 Potential complications of polycythemia vera is increased levels of circulating red blood cells, which increases the thickness or viscosity of the blood. This can be associated with higher risk of thrombus or clot formation leading to strokes, heart attacks, pulmonary embolism, and possibly death. Another complication of polycythemia vera is the potential transformation into a blood cancer (leukemia), excessive bleeding (hemorrhage), or clotting problems. Because of high turn over of blood cells in polycythemia, the excretion of the by products of red blood cell degradation may over burden the kidneys and result in kidney dysfunction, kidney stones, and gout. Complications of secondary polycythemia are typically related to those of the underlying disease. For example, chronic hypoxia from severe lung disease may be complicated by right sided heart failure and pulmonary hypertension. Chronic heart failure can lead to generalized swelling or edema (anasarca), low blood pressure, kidney dysfunction, and poor functional status. In neonatal (infant) polycythemia, increased blood thickness or viscosity can affect several organs due to poor blood flow. As a result, kidney dysfunction, intestinal problems, increased blood pressure in the lungs, and hypoxia may ensue.

Related Keyword terms:

,what is polycythemia,Red blood cell,polycythemia,red blood cells,erythropoietin secreting tumor,erythropoietin secreting tumors,what is polycythemia?,red cell,red blood cells increase,hemoglobin cell