Updated June 10, 2015.
Definition: This means you don't have enough platelets in your blood. The word is a combination of thrombocyte, which means "platelet," and penia, a word ending that means "deficiency."
Platelets are one of three main types of blood cells. The overwhelming majority of these cells are the red blood cells (erythrocyte), which bind to oxygen. The least common types are the white blood cells (leukocytes), which are essential to the body's immune system.
The last type are thrombocytes, which is better known as the platelet. These cells form in the bone marrow and then enter the blood circulation, where they are essential in clotting the blood. They do this by binding together and literally forming a "plug" in to the blood vessel opening to stop the bleeding.
When you don't have enough platelets, you are prone to bleeding, especially in the capillaries (the smallest of your blood vessels). Since this type of bleeding is internal, someone with thrombocytopenia must be observed closely.
There are many causes of thrombocytopenia. One cause is viral infection. It's also a common side effect from taking certain medications. For example, peginterferon and ribavirin sometimes cause thrombocytopenia in people treating chronic hepatitis C. Treatment for thrombocytopenia depends on its cause, but can include blood transfusions or taking additional medications.
Also Known As: Low Platelet Count