Mar 30, 2006

ITP and Platelet Antibodies

ITP frequently occurs after viral infection and in people with other autoimmune disorders. ITP is also known to occur after the use of certain medications including heparin used in the treatment of clotting disorders.

In ITP the immune system produces antibodies that destroy platelets. Several different platelet antibodies known to injure the platelet cell membrane are associated with ITP. Blood tests for platelet antibodies are used to diagnose ITP in people with low platelet counts. The bone marrow functions normally in ITP, that is, platelets are produced normally. They are destroyed by platelet antibodies in the blood circulation. Patients with ITP may also have lupus anticoagulant, particularly anticardiolipin or antiphospholipid antibodies.

The normal or reference range for platelets is 150,000-350,000. In moderate to severe ITP, when platelet counts fall below 20,000, patients are at risk for hemorrhage, a type of uncontrolled bleeding. The mortality rate from hemorrhage in ITP is 1 percent in children and 5 percent in adults. Higher mortality is seen in patients older than 60 years compared to patients less than 40 years old. In children, ITP is generally an acute condition, resolving within a few months in 80 percent of children. In children, males and females are equally affected. In adults, about 72 percent of patients are female.

Besides heparin, the medications quinine, quinidine, sulfa compounds, and alcohol can contribute to ITP. In children, ITP may develop after the administration of live vaccines.

Symptoms of ITP include increased bruising, heavy menstrual periods, retinal hemorrhages, gastrointestinal bleeding, normal coagulation tests (Protime and PTT), and gingival (gum) bleeding.

Treatment consists of corticosteroids, intravenous immunoglobulins, platelet transfusions, with best results if platelets are transfused after intravenous immunoglobulin therapy, and as a last resort spleen removal (splenectomy) in patients who do not respond to medical treatment.



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Comments

Nov 27, 2008 3:04 AM
Guest :
Hi Elaine
My father , who is 72 years old had a CBC done a few days ago in which the platelet count was found to be 32,000. The doctor then advised an array of tests like , LFT (Liver function test) , ANA , HIV etc. Now he says there is nothing abnormal and has advised to go for a bone marrow test . he says ot could be either of ITP or MDS . Can you help me understand what is going on .

Neel
Nov 28, 2008 4:24 PM
Elaine Moore :
Hi,
Out of all the lab tests we do, the platelet count is the one that's most often incorrect. This is because when there's trouble drawing blood and it takes a little longer the blood starts to clot and platelets are used up. Before having a bone marrow aspiration, I would think your doctor would first want to run another CBC and run tests for platelet antibodies. Some doctors will also try a course of corticosteroids to see if the platelet count rises.
Platelets can be low in several different disorders including some inherited conditions. Patients who have been on heparin often develop platelet antibodies and ITP. The antibodies destroy their antibodies. Platelet antibody tests can help diagnose this. Low platelets can cause increased bleeding, but the functional properties of platelets are more important than the count. People with low platelets can have normal hemostasis if their platelets are functioning properly. I'd ask about having the repeat CBC or platelet count along with tests for platelet antibodies and go from there. Best, Elaine
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