Low Platelet Count Often Related to Underlying Disorder

by David Steensma, M.D.

DEAR MAYO CLINIC:

I was told after my recent annual exam that my platelet count is low. Is this something I should be concerned about? What could be causing this?

ANSWER:

Low platelet count -- the medical term is thrombocytopenia -- can affect your blood's ability to clot. If platelet levels fall low enough, severe bleeding is possible. Often, the problem is related to an underlying disorder. Once that disorder is treated, platelet counts usually improve.

Bone marrow produces most of the blood cells in your body, including your platelets and red and white blood cells. Platelets are colorless blood cell fragments responsible for containing the damage when blood vessels are injured. They create microscopic "plugs" in vessel holes and release chemical messengers that trigger clotting.

Normally, between 150,000 and 450,000 platelets are found in one millionth of a liter (a microliter) of blood. Each platelet fragment lives for about 10 days, so your bone marrow is constantly replenishing your blood with new platelets.

If your blood platelet count falls below the normal range, complications may range from none at all to severe bleeding. Be sure to let your doctor know if you begin to bruise easily, have prolonged bleeding from cuts, spontaneously bleed from your nose or gums, or notice blood in your urine or stools. Another flag is a non-itchy rash of pinpoint-sized, reddish-purple spots, called petechiae. These typically occur in the lower legs, and are due to superficial bleeding into the skin.

The greater the decrease in platelet counts below normal, the higher the risk of bleeding. Depending on how low your platelet count is, it may be unsafe for you to undergo surgery or certain medical tests, such as colonoscopy. Severe bleeding can occur when platelet numbers fall below 30,000 per microliter of circulating blood. The greatest risk of severe bleeding is when the number falls below 10,000.

If you use blood-thinning drugs, such as warfarin or traditional nonsteroidal anti-inflammatory drugs (NSAIDS) such as aspirin, ibuprofen (Advil, Motrin, others) or naproxen (Aleve, Naprosyn, others), your doctor may direct you to discontinue using them if your count is below 70,000 to 80,000 per microliter.

Low platelet counts can usually be traced to one of the following:

Disorders that reduce platelet production by bone marrow: Various medical problems can affect bone marrow function, such as certain cancers, leukemia, bone marrow failure syndromes such as aplastic anemia, and some viral infections (such as HIV). Heavy alcohol use may also be a factor. There's also a long list of medications that can decrease platelet production. Since the chemical signal for the bone marrow to make platelets, thrombopoietin, is made in the liver, liver failure can also reduce platelet production.

Destruction of platelets: Several medical conditions are associated with premature loss of platelets from the circulation. These include immune system disorders such as lupus, rheumatoid arthritis, and idiopathic thrombocytopenic purpura (ITP), which occurs when antibodies mistakenly attack platelets. There are also non-immune mechanisms for platelets to get destroyed, such as accelerated clotting due to cancer, or a loose-fitting mechanical heart valve.

Platelets being trapped in the spleen: If your spleen enlarges due to a medical disorder, such as cirrhosis of the liver, the spleen may act like a sponge and trap too many platelets and cause a decrease in your circulating platelets.

Because you were discovered to have a low platelet count, your doctor may order more blood tests and possibly a bone marrow biopsy to help find a cause. If the low count is due to an identifiable cause, treatment of that condition will usually result in improvement in the thrombocytopenia. Should the problem be related to an adverse drug effect, low platelet counts usually improve once medication changes are made as directed by your doctor.

If the cause is ITP, treatment may include the use of corticosteroids, immune globulin infusions or medications -- such as cyclophosphamide (Cytoxan), azathioprine (Azasan, Imuran) or rituximab (Rituxan) -- that suppress the immune system and reduce antibody formation. ITP in adults is usually a chronic disease that comes and goes. Many people with ITP do well without bleeding for many years despite a chronically low platelet count. A new class of drugs, romiplostim (Nplate) and eltrombopag (Promacta), act like thrombopoietin to stimulate increased bone marrow production of platelets. These new drugs may be useful in patients with ITP whose condition does not respond well to other treatments.

Platelet concentrates may be given to help raise platelet numbers temporarily, especially if cancer or chemotherapy is related to the low count, or to prevent bleeding if you need surgery. Routine use of platelet transfusions may be limited by the formation of antibodies that can destroy new platelets.

David Steensma, M.D., Hematology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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