What Is Thrombocytopenia?

Thrombocytopenia (THROM-bo-si-to-PE-ne-ah) is a condition in which your blood has a low number of blood cell fragments called platelets (PLATE-lets). 

Platelets are made in your bone marrow along with other kinds of blood cells. They travel through your blood vessels and stick together (clot) to stop any bleeding that could happen if a blood vessel is damaged. Platelets also are called thrombocytes (THROM-bo-sites), because a clot also is called a thrombus. 
Overview

When your blood has a low number of platelets, mild to serious bleeding can occur. This bleeding can happen inside the body (internal bleeding) or on the skin.

A normal platelet count is 150,000 to 450,000 platelets per microliter of blood. A count of less than 150,000 platelets per microliter is lower than normal. But the risk for serious bleeding doesn't occur until the count becomes very low—less than 10,000 or 20,000 platelets per microliter. Milder bleeding sometimes occurs when the count is less than 50,000 platelets per microliter. 

Several factors can cause a low platelet count, such as: 
The body's bone marrow doesn't make enough platelets.
The bone marrow makes enough platelets, but the body destroys them or uses them up.
The spleen holds onto too many platelets. The spleen is an organ that normally stores about one-third of the body's platelets. It also helps your body fight infection and remove unwanted cell material.
A combination of the above factors.

How long thrombocytopenia lasts depends on its cause. It can range from days to years.

The treatment for this condition also depends on its cause and severity. Mild thrombocytopenia most often doesn't need treatment. If the condition is causing serious bleeding, or if you're at risk for serious bleeding, you may need medicines or blood or platelet transfusions. Rarely, the spleen may need to be removed. 
Outlook

Thrombocytopenia can be fatal, especially if the bleeding is severe or occurs in the brain. However, the overall outlook is good, especially if the cause of the low platelet count is found and treated.