Polycythemia vera

Definition

Secondary polycythemia is an acquired form of a rare disorder characterized by an abnormal increase in the number of mature red cells in the blood.

Secondary polycythemia is also called secondary erythrocytosis.

Description

Polycythemia means too many red blood cells. The resulting excess of red cells thickens the blood and impedes its passage through small blood vessels.

Secondary polycythemia usually affects people between the ages of 40 and 60.

Types of secondary polycythemia

Known as spurious polycythemia, stress polycythemia, or Gaisbock's syndrome, relative polycythemia is characterized by normal numbers of red blood cells but decreased levels of plasma (the fluid part of the blood). Overweight, middle-aged white men who smoke, have high blood pressure, and are on diuretic medicines to remove excess water from their bodies may develop Gaisbock's syndrome.

In smoker's polycythemia, the number of red blood cells is elevated. Plasma levels are abnormally low.

Causes & symptoms

Smoking, which impairs red blood cells' ability to deliver oxygen to body tissues, can cause secondary polycythemia. So can the following conditions:

• Carbon monoxide poisoning
• Chronic heart or lung disease
• Hormonal (endocrine) disorders
• Exposure to high altitudes
• Kidney cysts
• Tumors of the brain, liver, or uterus.

Causes of spurious polycythemia include:

• Burns
• Diarrhea
• Hemoconcentration (higher-than-normal concentration of cells and solids in the blood, usually due to becoming dehydrated or taking diuretics)
• Stress.

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.

Diagnosis

A very important part of diagnosing secondary polycythemia is differentiating it from primary polycythemia (also called polycythemia rubra vera or Vaquez' disease). Unlike secondary polycythemia, primary polycythemia cannot be traced to an underlying condition such as smoking, high altitude, or chronic lung disease.

Doctors diagnose polycythemia by measuring oxygen levels in blood drawn from an artery. A patient whose oxygen level is abnormally low probably has secondary polycythemia. Erythropoietin may also be measured. Levels of this hormone, which stimulates the bone marrow to produce red blood cells, may be normal or elevated in a patient with secondary polycythemia. Red blood cell mass is also frequently measured in diagnosing the disorder.

Imaging studies are sometimes performed to determine whether the spleen and liver are enlarged and to detect erythropoietin-producing kidney lesions. Other diagnostic procedures include chest x rays and an electrocardiogram (EKG).

Treatment

Secondary polycythemia is treated primarily by treating the underlying condition causing the disorder. For example, patients with Gaisbock's syndrome are often taken off diuretics and encouraged to lose weight. Lung disorders, such as chronic obstructive pulmonary disease (COPD), may cause secondary polycythemia; treating the lung disorder generally improves the polycythemia.

Some medications may also be taken to treat symptoms caused by polycythemia. For example, antihistamines can alleviate itching, and aspirin can soothe burning sensations and bone pain.

Until the underlying condition is controlled, doctors use bloodletting (phlebotomy) to reduce the number of red blood cells in the patient's body. In most instances, a pint of blood is drained from the patient as needed and tolerated, until the hematocrit (the proportion of red cells in the blood) reaches an acceptable level. Chemotherapy is not used to treat secondary polycythemia; however, it may be used to treat the primary form.

Prognosis

Curing or removing the underlying cause of this disorder generally eliminates the symptoms.

Further Reading

For Your Information

Books

• Berkow, Robert, ed. The Merck Manual of Medical Information: Home Edition. Whitehouse Station, NJ: Merck & Co., Inc., 1977.
• Fauci, Anthony S., ed. Harrison's Principles of Internal Medicine. New York, NY: McGraw-Hill, Inc., 1998.
• Rakel, Robert, ed. Conn's Current Therapy, 1998. Philadelphia, PA: W.B. Saunders Company, 1998.

  Other

• The Merck Manual: Secondary Erythrocytosis. http://www.merck.com/!!ux1b42ZA5ux1b42ZA5/pubs/mmanual/html/pjjgfckc.htm (3 June 1998).

Gale Encyclopedia of Medicine. Gale Research, 1999.