Secondary polycythemia is caused by excessive production of eryth-ropoietin. This may occur in response to a reduced amount of oxygen, which acts as a hypoxic stimulus, as in cigarette smoking, chronic obstructive pulmonary disease, or cyanotic heart disease, or in nonpathologic conditions such as high altitude. It can also result from certain hemoglobinopathies in which the hemoglo-bin has an abnormally high affinity for oxygen (eg, hemoglobin Chesapeake). Secondary polycythemia can also occur from neo-plasms (eg, renal cell carcinoma) that stimulate erythropoietin production.
Management of secondary polycythemia may not be necessary; when it is, it involves treating the primary problem. If the cause cannot be corrected (eg, by treating the renal cell carcinoma or improving pulmonary function), therapeutic phlebotomy may be necessary in symptomatic patients to reduce blood viscosity and volume.
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