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.

Causes, incidence, and risk factors 

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 (rare)  
  • Drugs (very rare)

Disorders that involve the breakdown of platelets include:

  • Immune thrombocytopenic purpura (ITP)  
  • Drug-induced immune thrombocytopenia  
  • Drug-induced nonimmune thrombocytopenia  
  • Thrombotic thrombocytopenic purpura  
  • Primary thrombocythemia  
  • Disseminated intravascular coagulation (DIC)  
  • Hypersplenism (an Enlarged spleen)


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

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

Signs and tests 

  • CBC shows low platelets  
  • Bone marrow aspiration or biopsy may be normal or may show low megakaryocytes (platelet precursors) or an infiltrating disease.  
  • PTT clotting study is normal  
  • PT clotting study is normal  
  • Platelet associated antibodies may be present

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

Expectations (prognosis) 
The outcome depends on the disorder causing the low platelet counts.


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

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

Prevention depends on the specific cause.

Johns Hopkins patient information

Last revised: December 7, 2012
by Mamikon Bozoyan, M.D.

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