Thrombocytopenia refers to an abnormally low blood-concentration of platelets, which are blood cells that promote blood clotting (coagulation) after injury to the lining of the blood vessels. When the concentration of platelets becomes too low, bruising and bleeding may occur. Cats with blood platelet concentrations of less than 40,000 per microliter of blood are at risk for spontaneous bleeding.
Abnormally low platelet numbers in blood can be caused by a variety of disease processes. These include failure to produce new platelets in the bone marrow, premature destruction of circulating platelets often by the body's own immune system, sequestration or storing of platelets in organs, and consumption of platelets at a rate that exceeds production in the bone marrow.
Cats of either gender, any age and any breed can suffer from thrombocytopenia.
The severity of bleeding associated with thrombocytopenia depends on how low the platelet numbers fall. In general, the lower the platelet count, the more likely bleeding is to occur.What to Watch For Small red spots on the white parts of the eyes (sclera), the gums or the skin
Bruises on the skin (ecchymoses)
Nose bleeds (epistaxis)
Diagnostic tests are needed to recognize thrombocytopenia and exclude other diseases. Tests may include:
A complete medical history and physical examination. Your veterinarian will ask about previous vaccinations and drug administration as possible factors in the development of thrombocytopenia.
A complete blood count (CBC or hemogram) including a platelet count to identify thrombocytopenia and anemia that may arise from bleeding
Serum biochemistry tests to evaluate for abnormalities in other organ systems and to evaluate the general health
Urinalysis to evaluate for infection, bleeding (hematuria) or protein loss that may occur as a complicating problem in some causes of thrombocytopenia
X-rays of the chest or abdomen to evaluate for the presence of other diseases such as infections or cancer that may be associated with thrombocytopenia.
Specific tests for infectious diseases, like tick-borne diseases such as Rocky Mountain Spotted Fever or ehrlichiosis.
Bone marrow aspiration to obtain a sample for laboratory analysis if there is concern that your cat's bone marrow may not be making adequate numbers of platelets or may have been invaded by cancer. This procedure often is performed under sedation with a local anesthetic to numb the biopsy site.
Other tests of blood clotting. Body-wide abnormalities in coagulation (disseminated intravascular coagulation) can result in massive consumption of platelets.
Immune system function tests if an immune-mediated disease is suspected. In this case the body fails to recognize the platelets as part of itself and attacks them as if they were foreign invaders. The body may consider the platelets as foreign invaders if they become coated with certain drugs or infectious agents.
Treatment for thrombocytopenia depends on the underlying cause of the low platelet count.
Unless your cat is bleeding, only the underlying cause of the thrombocytopenia is be treated. If a specific cause can be treated successfully, the blood platelet concentration soon returns to normal.
Corticosteroids (cortisone-like drugs) are often used to stop the immune system from destroying platelets.
Antibiotics, especially tetracyclines, often are prescribed until specialized test results for infectious disease are available. Tetracycylines are chosen because they are effective against bacterial agents called rickettsia that may cause thrombocytopenia, as in ehrlichiosis and Rocky Mountain spotted fever.
It is difficult to increase platelet numbers adequately by transfusion, and transfused platelets do not last very long – a few days at most. Transfusion of whole blood, which contains plasma and all blood cell types including red blood cells and platelets, or packed red cells, which contains red blood cells without plasma, may be necessary in the event of life-threatening hemorrhage or if your cat is anemic from previous blood loss. Platelet-rich plasma is difficult to prepare and is not widely available for cats.
Home Care and Prevention
Administer as directed all medications prescribed by your veterinarian. Keep your cat calm and confined indoors to prevent bleeding and bruising. Watch for signs of bleeding or bruising and call your veterinarian immediately if such signs occur or worsen.
Prevent tick bites whenever possible because ticks transmit the bacterial agents (rickettsia) that cause ehrlichiosis and Rocky Mountain spotted fever, diseases that cause thrombocytopenia. Use tick preventives and check your cat daily for ticks during warm weather. Other causes of thrombocytopenia are not preventable.