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Thrombocytopenia is any disorder in which there are not enough platelets. Platelets are cells in the blood that help blood to clot. This condition is sometimes associated with abnormal bleeding.

Thrombocytopenia is often divided into three major causes of low platelets:

1. Low production of platelets in the bone marrow
2. Increased breakdown of platelets in the bloodstream (called intravascular)
3. Increased breakdown of platelets in the spleen or liver (called extravascular)

Disorders that involve low production in the bone marrow include:

• Aplastic anemia
• Cancer in the bone marrow
• Infections in the bone marrow (very rare)
• Myelodysplasia

Use of certain drugs may also lead to a low production of platelets in the bone marrow, although this is rare.

Disorders that involve the breakdown of platelets include:

• Disseminated intravascular coagulation (DIC)
• Drug-induced nonimmune thrombocytopenia
• Drug-induced immune thrombocytopenia
• Hypersplenism
• Immune thrombocytopenic purpura (ITP)
• Thrombotic thrombocytopenic purpura

• Bruising
• Nosebleeds or bleeding in the mouth
• Rash (pinpoint red spots called petechiae)

Other symptoms may be present as well, depending on the cause of the condition. Mild thrombocytopenia can occur without symptoms.

Complete blood count (CBC) shows low number of platelets. Blood clotting studies (PTT and PT) are normal.

Other tests that may help diagnose this condition include:

• Bone marrow aspiration or biopsy
• Platelet associated antibodies

Treatment depends on the cause of the condition. In some cases, a transfusion of platelets may be required to stop or prevent bleeding.

The outcome depends on the disorder causing the low platelet counts.

Severe bleeding (hemorrhage) is the main complication. This can include:

• Bleeding in the brain (intracranial hemorrhage)
• Gastrointestinal bleeding (vomiting blood or blood in the stools )

Call your healthcare provider if you experience unexplained bleeding or bruising.

Prevention depends on the specific cause.

Goldman L. Ausiello D. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: WB Saunders; 2007:1291-1299.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and James R. Mason, MD, Oncologist, Director, Blood and Marrow Transplantation Program and Stem Cell Processing Lab, Scripps Clinic, Torrey Pines, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.