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Thrombocytopenia is any disorder in which there is an abnormally low amount of platelets. Platelets are parts of 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
  • Cirrhosis (chronic liver disease)
  • Folate deficiency
  • Infections in the bone marrow (very rare)
  • Myelodysplasia
  • Vitamin B12 deficiency

Use of certain drugs may also lead to a low production of platelets in the bone marrow. The most common example is chemotherapy treatment.

Disorders that involve the breakdown of platelets include:

  • Bruising
  • Nosebleeds or bleeding in the mouth and gums
  • 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.

Signs and tests

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:

Support Groups

Expectations (prognosis)

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

Calling your health care provider

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


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)
  • Nosebleeds

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


Prevention depends on the specific cause.


McMillan R. Hemorrhagic disorders: abnormalities of platelet and vascular function. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 179.

Review Date: 2/5/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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