Secondary polycythemia may result from increased production of erythropoietin. This hormone, which is possibly produced and secreted in the kidneys, stimulates bone marrow production of RBCs. This increased production may be an appropriate (compensatory) physiologic response to hypoxemia, which may result from:

Increased production of erythropoietin may also be an inappropriate (pathologic) response to renal disease (such as renovascular impairment, renal cysts, and hydronephrosis), to central nervous system disease (such as encephalitis and parkinsonism), to neoplasms (such as renal tumors, uterine myomas, and cerebellar hemangiomas), and to endocrine disorders (such as Cushing’s syndrome and pheochromocytomas). Rarely, secondary polycythemia results from a recessive genetic trait.

A patient with secondary polycythemia has an increased risk of hemorrhage due to problems with platelet quality, especially during surgery. Thromboemboli secondary to hemoconcentration may occur spontaneously; after prolonged immobility, as may occur with arthritic conditions or decreased mobility; or after surgery.

The patient’s history usually reveals shortness of breath (associated with emphysema). Inspection reveals a ruddy cyanosis of the skin and possibly clubbing of the fingers (in underlying cardiac or pulmonary disease). Hypoxemia is found without hepatosplenomegaly or hypertension, which constitutes a major difference between primary (vera) and secondary polycythemia.

Secondary polycythemia that isn’t caused by hypoxemia is usually an incidental finding during treatment for an underlying disease.

Laboratory results for secondary polythemia include: