Treating a low platelet count

On Call

July 09, 1996|By Dr. Simeon Margolis | Dr. Simeon Margolis,Special to The Sun

Just before my 50th birthday, little red spots appeared on my arms and legs. My doctor did blood tests and said that my platelet count is low. What are the spots? What causes a low platelet count and how can it be treated?

Pinpoint, flat and nontender spots, called petechiae, result from leakage of red blood cells into the skin. They can be caused by a skin disease or more often by a more generalized disorder that either interferes with blood clotting, leads to blockage of small blood vessels with clots or leaves these blood vessels too fragile.

The most common blood-clotting problem that produces petechiae is a low number of platelets or an abnormality in their function. Platelets (also called thrombocytes) are released from the bone marrow into the circulation where they are essential for normal clotting of blood following a cut or other injury. When the platelet count is too low, referred to as thrombocytopenia, bleeding into the skin can produce petechiae. Platelet counts less than about 20,000 per cubic millimeter (the normal number ranges from 150,000 to 350,000), can result in nosebleeds, excessive menstrual blood flow, and bleeding into vital areas such as the brain.

In adults, thrombocytopenia is caused by poor formation of platelets by the bone marrow, excessive trapping of platelets within an enlarged spleen, or increased destruction of circulating platelets. These different causes must be distinguished by diagnostic tests in order to choose the proper treatment. Poor platelet formation, which can result from replacement of the bone marrow by cancer cells or fibrous tissue, treatment of cancer with cytotoxic drugs, or unexplained failure of the bone marrow (aplastic anemia), can be recognized by removing a sample of bone marrow through a needle and syringe or by biopsy and examining it under the microscope. An enlarged spleen, often due to liver disease, can be identified on physical examination or by imaging techniques, possibly by X-ray. If the bone marrow examination is normal and the spleen is not enlarged, the thrombocytopenia is probably due to increased destruction of circulating platelets. Many factors, including immune abnormalities and sensitivity to a wide variety of medications, can lead to rapid destruction of platelets. If sensitivity to a drug is the cause, discontinuing it will usually return platelets to normal levels. When platelet levels are dangerously low, treatments include large doses of corticosteroids, transfusions with platelets, and removal of an enlarged spleen. Removal of a normal-sized spleen can at times raise platelet levels in individuals with chronically low platelet counts.

Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.

Pub Date: 7/09/96

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