Immune Thrombocytopenic Purpura
What Is It?
Immune thrombocytopenic purpura, previously known as idiopathic thrombocytopenic purpura, is a bleeding disorder caused by a low platelet count. ITP occurs when immune system cells produce antibodies against the platelets. Antibodies are proteins in the blood that the immune system uses to identify and neutralize foreign objects. After the antibodies attach to the platelets, the spleen destroys the platelets carrying those antibodies. With a decreased amount of antibodies, the blood has difficulty clotting, leading to unnecessary bleeding.
Symptoms & Warning Signs
Technically, ITP itself is asymptomatic, but the very low platelet count that it causes can lead to several visible and systematic symptoms, including the following:
- Abnormally heavy or prolonged menstruation
- Pinpoint red spots (petechiae) or a petechial rash
- Easy bruising
- Nosebleed or bleeding in the mouth or gums
- Brain hemorrhage
- Lower gastrointestinal bleeding
Tests & Diagnosis
There is currently no single blood test for immune thrombocytopenic purpura, so doctors may diagnose ITP through a process of exclusion. Although the spleen is a large contributor to the ITP disorder because it kills the antibody-laced platelets, ITP patients do not typically show signs of spleen enlargement. Also, bleeding time, though typically prolonged in ITP patients, is not a factor in ITP diagnosis, because normal bleeding time can occur in blood disorder patients.
A normal platelet count is anywhere from 150,000 to 450,000 platelets per microliter of blood, so anything below that range can indicate a platelet deficiency. After determining that there are no physical signs other than those of bleeding and that there are no blood abnormalities other than the low platelet count common in ITP, the clinician must exclude any secondary causes. These can include leukemia, blood thinners, lupus, cirrhosis, HIV, hepatitis C, congenital disease and many others. However, these secondary causes are only present in approximately 5 to 10 percent of suspected ITC cases. Following the exclusion of these factors, doctors may perform a bone marrow aspiration and biopsy, as patients with ITP have a normal to increased level of megakaryocytes, or bone marrow cells responsible for producing blood platelets.
In children, a bone marrow examination is not required to diagnose ITP, because many children with the disorder have an increased number of lymphocytes on a peripheral blood smear, reflecting a recent viral illness.
Prevention & Treatment
Doctors usually determine which ITP patients most likely need treatment. Typically, patients with platelet counts under 20,000 require treatment, and those with counts above 50,000 generally do not. For patients with platelet levels between 20,000 and 50,000, the necessity for treatment is determined by personal doctors on a case by case basis.
ITP is most common in children ages 1 to 6 (more so in boys than in girls) and in middle-aged adults, most frequently women. For adults, the disease is usually chronic, but for children, it typically occurs following a viral infection. In children, ITP usually goes away without treatment. For children who still show symptoms and are unresponsive to typical treatment after six months, doctors may determine that a bone marrow transplant is necessary. Treatments for adults vary by case and doctor recommendation, and can include the following:
- Steroids, when administered intravenously, typically act as emergency treatment. Once platelet counts have increased, doctors may administer oral steroids.
- Anti-D, or Rho(D) immune globulin, can be used on Rh-positive ITP patients, but it is expensive and usually only produces short-term improvement.
- Steroid-sparing agents are typically used with caution, as they can present intense side effects. Because steroid-sparing agents are short-term helpers, doctors may use them to help keep ITP patient's platelets up before a surgery.
- Thrombopoietin receptor agonists are pharmaceutical agents that stimulate platelet production. Some doctors may consider them as treatment for long-term or chronic ITP patients.
- Surgery, more specifically a splenectomy, may be considered to curtail platelet destruction on the part of the spleen. However, the procedure is potentially dangerous to ITP patients due to increased chances of heavier bleeding during the operation.
- Experimental and novel agents have recently been used by some doctors. These include dapsone, rituximab and a kinase inhibitor. The use of these typically requires patient approval, as they are not currently considered standard ITP treatments.
- Platelet transfusion is an emergency treatment for ITP patients that usually only produces a platelet count increase for the short-term.
Each ITP treatment is subject to approval from a licensed doctor, typically a hematologist, and holds its own benefits and risks. An ITP patient should consult their physician before moving forward with any line of treatment.
Currently, there are no known preventative measures regarding ITP. However, patients with ITP are generally instructed by a doctor to avoid taking aspirin, ibuprofen and warfarin, because these drugs can interfere with platelet function or blood clotting, causing more bleeding.