Immune-Mediated Thrombocytopenia in Dogs

Platelets cannot be replenished quickly enough by the body. It can be difficult to diagnose and many veterinarians will refer you to a specialist in order to properly diagnose and treat immune-mediated thrombocytopenia. The American Cocker Spaniel, Standard Poodle, Miniature Poodle, Toy Poodle, Old English Sheepdog, German Shepherd Dog and Labrador Retriever are predisposed to immune-mediated thrombocytopenia. Middle aged dogs are more likely to be diagnosed with immune-mediated thrombocytopenia.

Immune-mediated thrombocytopenia in dogs attacks the dog’s own blood platelets and is a very serious disease. Antibodies will bind to the surface of platelets causing the affected platelets to prematurely destruct.

Immune-mediated thrombocytopenia is a serious condition and if you see any of these symptoms, contact your veterinarian immediately for a thorough physical exam and testing. 

• Abnormally rapid breathing
• Weakness
• Lethargy
• Bruising
• Bleeding from the gums
• Bleeding from the nose
• Tarry stools
• Pale gums
• Difficulty breathing
• Anorexia or lack of appetite
• Sudden death

Types

Immune-mediated thrombocytopenia in dogs can be classified in two categories.

Primary Immune-mediated Thrombocytopenia

Also known as idiopathic thrombocytopenic purpura, primary immune-mediated thrombocytopenia is an autoimmune disorder where the antibodies attack portions of the platelet membrane. There is no underlying disease causing the immune-mediated thrombocytopenia. 

Secondary Immune-mediated Thrombocytopenia

The antibodies are being bonded to antigens and then absorbed into the platelet surface. Secondary immune-mediated thrombocytopenia is the result of an underlying disease.

There are numerous causes of immune-mediated thrombocytopenia and your veterinarian will try to determine the exact cause to ensure that the treatment plan put in place will address the cause.

Vaccines

Although rare, there have been some cases where dogs have developed immune-mediated thrombocytopenia after receiving a vaccine.

Neoplasia

Immune-mediated thrombocytopenia is very commonly associated with hematopoietic and solid neoplasms. This includes mammary adenocarcinoma, lymphoma, fibrosarcoma, nasal adenocarcinoma and mast cell tumors. 

Infections

Bacterial, viral, parasitic or protozoal infections within the body can cause destruction of blood platelets. The destruction of these platelets can cause immune-mediated thrombocytopenia.

Autoimmune Diseases

Other autoimmune diseases in dogs can trigger immune-mediated thrombocytopenia. Systemic lupus, rheumatoid arthritis and immune-mediated hemolytic anemia are some of the more common autoimmune diseases that can cause immune-mediated thrombocytopenia.

Drug Therapies

It has been found that any drug can cause immune-mediated thrombocytopenia but there are certain drugs that have a higher incidence of causing it. These drugs include cefazedone, auranofin and trimethoprim-sulfonamide combinations.

Diagnosing immune-mediated thrombocytopenia is a process of elimination and determining the cause of the symptoms. Your veterinarian may refer you to a specialist for a definitive diagnosis and specialized treatment plan.

Clinical Symptoms

Your veterinarian will evaluate your dog’s symptoms and try to rule out other diseases. Most of the time, a dog is presented to them with signs other than severe bleeding, therefore, trying to determine the cause of the symptoms can be frustrating.

Physical Exam and Medical History

Your veterinarian will do a thorough physical examination of your dog. An evaluation of your dog’s medical history will help determine if there are any recent changes such as new medications or vaccinations. Try to give your veterinarian as much information as possible, including daily routines, recent traveling and changes in activities. 

Diagnostic Testing

A CBC, or complete blood count, will be ordered to determine the amount of blood platelets being produced by the body. Other tests that may be performed include a blood smear, serum chemistry profile, heartworm antigen testing, and coagulation profile. Blood samples will be collected by atraumatic venipuncture to prevent the activation of clotting factors or minimize platelet clumping. Confirmation based on a CBC test and blood smear examination can be done if the immune-mediated thrombocytopenia has progressed to the point of rapid platelet depletion. 

Urinalysis

A urinalysis is conducted to rule out fungal disorders or rickettsial. Urine must be collected by free catch.

Imaging

To determine if the underlying cause is a neoplasia a thoracic and abdominal radiograph and an abdominal ultrasonography will be ordered. 

Bone marrow aspiration

Bone marrow aspiration is only needed if concurrent leukopenia, with or without anemia, is not present. If performed, it may show an underlying cause that is not apparent through a clinical examination.

Your veterinarian will create an individualized treatment plan for your dog. These treatment plans are often aggressive and require continual care, therefore, hospitalization is usually required.

Immunosuppressive drugs such as steroids, cyclosporine and azathioprine have been effective in treatments. Immunosuppressive drugs will help control your dog’s immune system response to the depletion of blood platelets.

Supportive care may be necessary depending on how ill your dog has become. Oxygen support and IV fluids will be given. Blood transfusions may be required if your dog has become anemic.

In the case of secondary immune-mediated thrombocytopenia, the underlying cause must be treated as well as the thrombocytopenia. Your dog may need to remain on supportive care while the underlying cause is being addressed.

Immunosuppressive drugs may need to be continued for several months. Your dog can be weaned from the medications upon conclusion of the entire treatment plan. Drug therapy may be required for the rest of your dog’s life to ensure that your dog’s blood platelets are not decreasing. Most dogs, when treated aggressively and diagnosed in time, can live normally following treatments. 

Any vaccines or medications that were found to be the cause of immune-mediated thrombocytopenia in your dog should be avoided for the rest of his life. All immune system stimulants, such as vaccinations, should be avoided also.

Be sure to listen carefully to your veterinarian and follow all treatments set for your dog to ensure recovery from immune-mediated thrombocytopenia. All medications should always be used as prescribed and any concerns should be directed to your veterinarian.