Immune Mediated Thrombocytopenia
Overview:
The definition of thrombocytopenia is a low platelet count. Many diseases can cause the platelet count to decrease including Ehrlichia, Rocky Mountain Spotted Fever, leptospira, many drugs, irradiation therapy, hemangiosarcoma, lymphoma, leukemia, and FIP. A patient is diagnosed with immune-mediated thrombocytopenia if none of the above illnesses can be found, but the platelets are being destroyed in the bloodstream.
Causes:
The cause of primary immune-mediated thrombocytopenia is unknown. It is more common to have an underlying disease process outlined above to cause destruction of platelets.
Symptoms:
Since platelets are required for blood coagulation, most clinical signs are related to bleeding. Pets will be lethargic, weak, and have a poor appetite. Nose bleeds, blood in the stool, and small hemorrhages on the skin or gums (petechiae) are common findings. Sometimes, the signs of bleeding are internal and can not be seen.
Treatment:
Regardless of the cause of the platelet destruction, patients are routinely started on high doses of prednisone and gastric protectants such as sucralfate or cimetidine. Any unnecessary medications (joint supplement, vitamins, NSAIDs) should be discontinued during the treatment phase as they can worsen the disease. All patients need to be under strict confinement, sometimes in the hospital, due to the increased risk of spontaneous bleeding.Numerous tests should be performed to rule out underlying disease processes. Tick-borne diseases (Ehrlichia, Rocky Mountain Spotted Fever) are very common causes of thrombocytopenia so doxycycline is routinely added to the therapy while tests are being performed. Cats should be tested for feline leukemia and FIV. Some pets (~20%) that have immune-mediated thrombocytopenia also concurrently have immune-mediated anemia. The patient has a 50/50 chance of relapsing in the future meaning that many times a patient will only have one episode of thrombocytopenia even if a cause can not be found and treated appropriately.
