Patient Information Resource:
Benign Hematologic (Blood) DisordersA collaborative project of the Arizona Telemedicine Program, the Arizona Health Sciences Library and the Arizona Cancer Center.
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Erythrocytosis/Polycythemia
A. What Is Erythrocytosis?
Erythrocytosis is defined as an excess of erythrocytes, or red blood cells (RBCs). RBCs carry oxygen to the body. When RBC levels are low, the body’s tissues cannot obtain enough oxygen.
RBCs in the blood are measured by the hematocrit (the percentage of the blood volume made up of RBCs) or by the hemoglobin (the essential oxygen-carrying protein in the RBC). Erythrocytosis occurs if either of these values is elevated. The normal limits on these blood values for males and females respectively are 52% and 47% for the hematocrit, and 17.7 g/dl and 15.7 g/dl for hemoglobin concentration.
B. Causes and Risk Factors
There are several different kinds of erythrocytosis, and each has its own set of causes and risk factors.
Relative Polycythemia. Some patients appear to have an excess of RBCs due to a loss of volume in the liquid portion of the blood, the plasma. This may be due to dehydration, diuretics (substances causing an increased loss of water through the urine, such as caffeine), burns, stress, and high blood pressure.
Primary polycythemia, or polycythemia vera. Primary polycythemia is a myeloproliferative disorder in which the RBC count increases without being stimulated by the red blood cell stimulating hormone, erythropoietin (EPO). For more on this disorder, please see Myeloproliferative Disorders.
Secondary polycythemia. In secondary polycythemia, the increase in RBC counts is due to an increase in the RBC stimulating hormone, EPO. Potential causes of this include: low blood oxygen, caused by heart disease or high altitude; continual exposure to carbon monoxide (heavy smoking of cigars or cigarettes); congenital (hereditary) disorders producing an abnormal hemoglobin or an overproduction of EPO; and diseases such as kidney disease.
C. Signs and Symptoms
Symptoms include: easy bruisability, purpura (purplish areas of the skin where hemorrhage has occurred), blood in the stool, blood clots, painful erythema (redness of the skin) and warmth in parts of the limbs, blackening of the fingers or toes (necrosis), fever, heat tolerance, weight loss, and itching.
D. Diagnosis
The patient history and physical examination is helpful to the physician in suggesting erythrocytosis. Ultimately, erythrocytosis is detected by blood studies evaluating hematocrit, hemoglobin, red cell count, and red cell mass. If these are elevated, the patient has erythrocytosis. Based on the patient history and blood volume tests, the physician may be able to differentiate between the different types of erythrocytosis.
E. Treatment
For relative polycythemia and secondary polycythemia, treatment must address the underlying problem. In relative polycythemia, the patient must avoid diuretics and drink fluids to replenish the liquid portion of the blood2. In secondary polycythemia, the treatment varies depending on the cause of the problem. For the treatment of polycythemia vera, see Myeloproliferative Disorders.
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Updated: October 30, 2000