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 (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
• Disseminated intravascular coagulation (DIC)
• Hypersplenism

• 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.

• 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