Autoimmune disease attacks platelets in blood

2008-06-04T00:00:00Z Autoimmune disease attacks platelets in bloodby MARK JERGENS, MD - for the Ravalli Republic Ravalli Republic

The other day a co-worker indicated to me that as a child she had been diagnosed with a blood disorder called ITP, or idiopathic thrombocytopenic purpura. She said that she took hydrocortisone medication to get over the disease; but no one ever figured out why she “got” the disease.

Idiopathic Thrombocytopenic Purpura (ITP) is an autoimmune disease that causes the body’s own immune system to attack and kill one of the components of blood - platelets. Platelets are extremely small, colorless cells of the blood, that stick together to form initial “clot,” after an injury, to prevent more bleeding. Platelets are also known as thrombocytes. An abnormally low number of platelets in the blood is known as thrombocytopenia.

Purpura is a type of “rash” caused by multiple very small areas where blood has leaked from the capillaries under the skin. It has the appearance of very small reddish dots under the skin that vary in size from pinpoint to dime size. The number of reddish dots or extent of the “rash” depends on the severity of the ITP.

Lastly, the term idiopathic means, “without a known cause.”

Put together, ITP is a disease of unknown cause (idiopathic), resulting in an abnormally low number of circulating platelets (thrombocytopenia), because the body’s own immune system attacks them. The abnormally low number of thrombocytes allows spontaneous bleeding from capillaries under the skin, creating multiple reddish dot-like rash (purpura).

The actual mechanism of the abnormally low number of platelets occurs because the body’s immune system is triggered by some foreign protein - like a virus, bacteria or even a medication, to make antibody which attacks and adheres to the platelets. The platelets that have this antibody adherent to them are then removed from the blood by the spleen - an organ in the abdomen that removes abnormal blood cells. With ITP, the platelets are “tagged” by antibody, and removed by the spleen faster than the body can produce them, so the number of platelets circulating in the blood drops.

There are two types of ITP - acute and chronic. Acute ITP is much more common, occurs almost exclusively in children, almost always following a viral infection. Acute ITP last less than six months and seldom requires specific treatment. The disease abates on its own over a relatively short time. Chronic ITP last longer than six months, is less common, and usually affects adults. Chronic ITP much more often requires treatment.

Since the pathologic problem with ITP is loss of platelets whose function is to initiate blood clotting after an injury; it is not surprising that the primary problem people who have ITP suffer is excessive bleeding. A healthy adult has between 150,000 and 450,000 platelets at any given time. Generally people don’t get serious bleeding problems with platelet counts above 50,000; and generally internal bleeding does not occur, without injury, until platelet counts approach 10,000.

As previously indicated, children with acute ITP seldom develop bleeding complications, and if bleeding occurs, it is usually limited to nose bleeding, bleeding from gums or easy bruising.

However, adults with chronic ITP have a clinical picture that (corresponding with their platelet count) varies from no symptoms to spontaneous internal hemorrhage. Internal bleeding, especially in the brain, causes the highest risk of serious injury or death.

The diagnosis of ITP is made by the combination of several blood tests, including:

• A complete blood count (CBC) which reports the numbers of cells in the blood - platelets, red blood cells (RBCs) and white blood cells (WBCs) respectively

• A blood smear which allows the examination of the blood elements under a microscope

• A bone marrow examination which reveals whether the thrombocytopenia is caused by too little production versus too much destruction.

Once diagnosed, there are a number of treatment options, if treatment is needed:

• Prednisone - this potent anti-inflammatory medicine reduces the immune system’s ability to produce antibodies to “tag” onto platelets. Most people get fairly dramatic improvement with prednisone; however 50 to 70 percent of the time, the disease recurs after the prednisone is discontinued.

• Intravenous immunoglobulin - patients with very low platelet counts or who must undergo elective surgery, when elevation of the platelet count is needed over several days, can receive this IV medication. However, just as the onset of effect is rapid, so is the return to a normal platelet count - usually within weeks.

• Intravenous platelets - platelets from blood donors can be packaged and transfused intravenously. Generally this is done in situations of serious bleeding or emergency surgery when elevation of the platelet count needs to be immediate.

• Surgical removal of the spleen (splenectomy) - this is a major surgery and therefore reserved for people with chronic ITP that is unresponsive to medication. Splenectomy, in addition to the morbidity of major surgery, also puts people at risk for certain types of infections for the remainder of their life.

• Chronic immunosuppressant medications such as Cytoxan, Ritaxan or Imurran are less commonly used. These medications can be considered in people who have not responded to prednisone or splenectomy (or who are not candidates for major surgery).

Fortunately, most people with ITP never require any treatment; however, it is very important for anyone with ITP to practice preventive self-care including:

• Avoiding platelet inhibiting medications - primarily aspirin and ibuprofen, but also prescription medications such as Plavix. Likewise anticoagulation medications (blood thinners) such as Heparin and Coumadin should be avoided.

• Limiting alcohol consumption which can also impair blood clotting by its effect on the liver.

• Minimizing the potential for injuries which can cause bleeding.

Comments can be sent to Mark Jergens, MD, MHA, Chief Medical Officer, Marcus Daly Memorial Hospital, 1200 Westwood Dr., Hamilton, MT, 59840.

Copyright 2016 Ravalli Republic. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

No Comments Posted.

Add Comment
You must Login to comment.

Click here to get an account it's free and quick