Secondary Polycythemia

Secondary polycythemia - also called reactive polycythemia - is characterized by excessive production of circulating red blood cells (RBCs) due to hypoxia, tumor, or disease. It occurs in about 2 out of every 100,000 persons who live at or near sea level; incidence increases among people who live at high altitudes.

Causes

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

• chronic obstructive pulmonary disease
• hemoglobin abnormalities (such as carboxyhemoglobinemia, which occurs in heavy smokers)
• heart failure (causing a decreased ventilation­perfusion ratio)
• right-to-left shunting of blood in the heart (as in transposition of the great vessels)
• central or peripheral alveolar hypoventilation (as in barbiturate intoxication or pickwickian syndrome)
• low oxygen content of air at high altitudes.

Symptoms

Weakness, headaches, and fatigue are usually the first symptoms of secondary polycythemia . Patients may feel lightheaded or experience shortness of breath .

Visual disturbances associated with this disorder include distorted vision, blind spots, and flashes of light. The gums and small cuts are likely to bleed, and the hands and feet may burn. Extensive itching often occurs after taking a bath or shower.

Pain in the chest or leg muscles is common. The face often becomes ruddy, then turns blue after exercise or other exertion. Confusion and ringing in the ears ( tinnitus ) may also occur.

Diagnostic tests 

Laboratory results for secondary polycythemia include:

• increased RBC mass, with increased hematocrit, hemoglobin levels, mean corpuscular volume, and mean corpuscular hemoglobin
• elevated urine erythropoietin levels
• increased histamine levels
• decreased or normal arterial oxygen saturation.

Treatment

The goal of treatment is correction of the underlying disease or environmental condition. In severe secondary polycythemia when altitude is a contributing factor, relocation may be advisable. If secondary polycythemia has produced hazardous hyperviscosity, or if the patient doesn't respond to treatment for the primary disease, reduction of blood volume by phlebotomy or pheresis may be effective.

Emergency phlebotomy is indicated for prevention of impending vascular occlusion and before emergency surgery. In the latter case, removal of excess RBCs and reinfusion of the patient's plasma is usually advisable.

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