ASK DR. BAUGHAN                                             April 16, 1999

THE OTHER BLOOD CELL

“Would you print some information about ITP?” a reader asked.

Most people are familiar with two types of cells in our blood, red blood cells and white blood cells.  The red blood cells carry oxygen to our brains, muscles and other tissues.  The white blood cells fight infections.  Less well known are the third major type of red blood cell, platelets.  Platelets are much smaller.  They are so small they do not have a nucleus, and under the microscopic compared to the other cells, they look like small flecks of debris.  They have a crucial role in our bodies, though.  When we have a cut or when a blood cell inside starts to leak, the platelets clump together to begin a clot to plug up the site of bleeding.  Since we are mostly made of water, we are leaky creatures, so we need lots of platelets.

There are only a handful of diseases associated with platelet problems.  As you might expect, we have trouble if we have too many or too few platelets.  For such small cells, the diseases of platelets have very big names.  ITP stands for Idiopathic Thrombocytopenic Purpura.  “Idiopathic” means we do not know the cause (not because we are idiots).  Thrombocytopenic (rhymes with Rambo-psycho-manic) means “low platelet count.”  And Purpura means a spotty rash from blood under the skin.  The rash is usually the first and sometimes the only sign of the disease.  The rash is most often tiny red spots the size of a pencil point clustered on the lower legs, around pressure spots such as under the belt line, and sometimes in the cheeks of the face.  There are hundreds of spots.  If the condition persists, the spots may merge together and become blotchy.  The danger with the disease is uncontrolled bleeding, either from cuts or inside the digestive tract, or especially inside the brain.  Remarkably, although we normally have several hundred thousand platelets per cubic millimeter of blood (a small drop), bleeding rarely occurs unless the platelet count is less than 20,000.

Platelets are made in the bone marrow.  They are spit out of big mother-ship platelet factories called megakaryocytes (mega-carry-o-sites) and flow into the blood stream.  They may be stored in the spleen.  They only last for 4-10 days, so we need a constant re-supply.  In ITP, something destroys them before their time.  Sometimes they last only 30-60 minutes.  The megakaryocytes may speed up production, but they can’t keep up.  What destroys them?  In 1951 we learned that it was a protein in the blood stream that attacks them when Dr. William Harrington infused himself with plasma from a patient with ITP.  His platelet count temporarily dropped very low.

Treatment varies with severity.  If the platelet count is not too low, no treatment may be necessary other than avoidance of injuries.  With moderate bleeding under the skin, steroid medicine such as Prednisone is often given.  This slows production of the protein antibody that attacks the platelets, and slows the action of white blood cells that then attack the platelet-antibody complex.  Many times this gives a long remission, and the steroid medicine can be stopped.

The protein antibody is mostly produced in the spleen.  If ITP comes back, removing the spleen is often recommended to shut off production of the antibody.  If the person could not tolerate surgery or refuses, other medicines to stop the antibody production are attempted.  Unfortunately, these medicines stop production of other “good” antibodies as well, so they have risks with them.  One good antibody to have is against the Pneumococcal bacteria, so a person should have a Pneumococcal vaccine before a splenectomy.

Although from ancient times we have a creepy feeling if “something is wrong with our blood,” most people live normal lifetimes with ITP.  There is a 1-5% risk of death from it, which is certainly serious, but with attention and on-going monitoring, a person can hope for a reasonably unhampered life.