If for any reason your blood platelet count falls below normal, the condition is called thrombocytopenia. Normally, you have anywhere from 150,000 to 450,000 platelets per microliter of circulating blood. Because each platelet lives only about 10 days, your body continually renews your platelet supply by producing new platelets in your bone marrow.

Thrombocytopenia can be inherited or it may be caused by a number of medications or conditions. Whatever the cause, circulating platelets are reduced by one or more of the following processes: trapping of platelets in the spleen, decreased platelet production or increased destruction of platelets.

Trapped platelets

The spleen is a small organ about the size of your fist located just below your rib cage on the left side of your abdomen. Normally, your spleen works to fight infection and filter unwanted material from your blood. An enlarged spleen — which can be caused by a number of disorders — may harbor too many platelets, causing a decrease in the number of platelets in circulation.

Decreased production of platelets

Platelets are produced in your bone marrow. If production is low, you may develop thrombocytopenia. Factors that can decrease platelet production include:

  • Leukemia
  • Some types of anemia
  • Viral infections, such as hepatitis C or HIV
  • Chemotherapy drugs
  • Heavy alcohol consumption

Increased breakdown of platelets

Some conditions can cause your body to use up or destroy platelets more rapidly than they're produced. This leads to a shortage of platelets in your bloodstream. Examples of such conditions include:

  • Pregnancy. Thrombocytopenia caused by pregnancy is usually mild and improves soon after childbirth.
  • Immune thrombocytopenia. This type is caused by autoimmune diseases, such as lupus and rheumatoid arthritis. The body's immune system mistakenly attacks and destroys platelets. If the exact cause of this condition isn't known, it's called idiopathic thrombocytopenic purpura. This type more often affects children.
  • Bacteria in the blood. Severe bacterial infections involving the blood (bacteremia) may lead to destruction of platelets.
  • Thrombotic thrombocytopenic purpura. This is a rare condition that occurs when small blood clots suddenly form throughout your body, using up large numbers of platelets.
  • Hemolytic uremic syndrome. This rare disorder causes a sharp drop in platelets, destruction of red blood cells and impairment of kidney function. Sometimes it can occur in association with a bacterial Escherichia coli (E. coli) infection, such as may be acquired from eating raw or undercooked meat.
  • Medications. Certain medications can reduce the number of platelets in your blood. Sometimes a drug confuses the immune system and causes it to destroy platelets. Examples include heparin, quinine, sulfa-containing antibiotics and anticonvulsants.
March 31, 2015