What is thrombocytopenia?

Causes and Symptoms

Thrombocytopenia occurs when platelets are lost from the circulation faster than they can be replaced by the bone marrow where they are produced. It may result from either a deficiency in platelet production or an increased clearance rate from the blood. Clinically, thrombocytopenia is defined as a platelet count less than the normal levels of 150,000 to 350,000 per microliter of blood.

There are several specific causes of thrombocytopenia. In artefactual thrombocytopenia, antibodies in a person’s blood cause platelets to stick together and cause a falsely low platelet count. In congenital thrombocytopenia, one of several rare genetic diseases causes low platelet counts. Another cause of thrombocytopenia is impaired platelet production, such as in leukemia
or lymphoma, where the number of some other cell type in the bone marrow is increased, leaving fewer megakaryocytes for platelet production. Alternatively, the rate of platelet destruction can be increased as in disseminated intravascular coagulation (DIC), in which the blood clotting process is inappropriately activated. Antibodies in the blood, produced because of infections such as human immunodeficiency virus (HIV) or rheumatoid arthritis, can cause platelet
removal. Idiopathic or immunologic thrombocytopenic purpura (ITP) causes thrombocytopenia through destruction of platelets by the patient’s immune system. Thrombocytopenia can also be attributable to an abnormal distribution of platelets, as when platelets are sequestered in a patient’s enlarged spleen. Thrombotic thrombocytopenic purpura (TTP) is a disease resulting in thrombocytopenia. Platelets clump together in areas of clots to the extent that there are fewer platelets in other parts of the body. Finally, a massive transfusion of red blood cells can dilute platelets to thrombocytopenic levels.

Thrombocytopenia can cause excess bleeding and thus has several notable symptoms. Petechiae, rashes, and frequent bruising can appear on the skin, provoked by minor injury or pressure. Bleeding from wounds or body cavities may occur. At extremely low platelet counts, those below 20,000 per microliter, spontaneous bleeding occurs. The spleen and liver may be enlarged and sensitive to the touch if the thrombocytopenia is caused by splenic activity. Impaired clotting may cause blood to appear in the stool, urine, vomit, or sputum. Thrombocytopenic patients may also experience anemia, feel fatigued, or exhibit an elevated heart rate.

Low platelet counts increase the risk of bleeding, which becomes particularly dangerous when the count falls below 10,000 per microliter. Bleeding from the nose and gums is quite common. Serious hemorrhage can occur at the retina in the back of the eye, threatening vision. The most critical bleeding complication posing a risk to life is spontaneous bleeding in the head or in the lining of the gut.

Treatment and Therapy

The primary treatment for thrombocytopenia is to address the underlying cause of the deficiency. This is not always possible. If significant blood loss has occurred, then red blood cell or platelet transfusion may be necessary. However, in the condition of thrombotic thrombocytopenia purpura, the use of platelet concentrates is quite hazardous. Platelet growth factor can be used to stimulate increased platelet production in the bone marrow. Additionally, certain drugs such as aspirin and ibuprofen are to be avoided since they are known to cause antiplatelet activity.

If an infection is suspected as the cause of thrombocytopenia, then treatment such as antibiotics for the specific infection is often initiated. Some viral infections such as glandular fever caused by Epstein-Barr virus
have no specific treatment, and only close monitoring is applied. If the thrombocytopenia is caused by the presence of cancer
cells in the bone marrow, then treatment such as chemotherapy or radiotherapy is directed at the abnormal cells. In such cases, the bone marrow may become damaged and blood platelet counts further lowered. Platelet transfusions are then given to prevent bleeding, until either the platelet count reaches acceptable levels or the bone marrow recovers its ability to produce sufficient numbers of platelets.

Perspective and Prospects

Prior to the development of plasma exchange as an effective treatment in the 1970s, the mortality from thrombotic thrombocytopenic purpura–hemolytic uremic syndrome (TTP-HUS) was 90 percent. During those times, diagnosis was made using five clinical observations, including thrombocytopenia and fever. The availability of effective plasma exchange treatment has lowered the mortality rate to 20 percent. Early diagnosis is important, with thrombocytopenia and one other criterion the only requirements for initiation of treatment since 1991.

At the start of the twenty-first century, the treatment of children with idiopathic or immunologic thrombocytopenic purpura remained controversial. Platelet counts can be increased by treatment with corticosteroids, but clinical outcomes may not improve. Because most children spontaneously recover from severe thrombocytopenia in several days to weeks, only supportive care is sometimes recommended in this case.

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