Immune Mediated Thrombocytopenia in Dogs
Key takeaways
Immune-mediated thrombocytopenia (IMT) in dogs is a condition resulting from a significant decrease of platelets (thrombocytes) in the blood which is facilitated by the immune system.
- IMT can be either primary and idiopathic, or a secondary condition resulting from an infectious, parasitic, or immune-mediated disease
- Thrombocytopenia can lead to spontaneous bleeding and delayed clotting
- Mild IMT is asymptomatic, but common signs are nosebleeds, coughing, black and tarry stools, and pale gums
- Diagnosis involves bloodwork to evaluate the number of platelets present and look for an underlying cause
- A definitive diagnosis for IMT is usually through elimination
- Treatment consists of long-term corticosteroid therapy along with supportive care and blood transfusions
- In cases of secondary IMT, addressing the underlying condition is also necessary
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A closer look: Immune Mediated Thrombocytopenia in Dogs
Platelets are produced in the bone marrow and assist with clotting. There are many possible causes of a low platelet count (thrombocytopenia), but immune-mediated thrombocytopenia (IMT) is caused by immune system destruction of platelets.
IMT is uncommon in dogs. It is potentially life-threatening and can be associated with other severe illnesses that might require immediate medical attention. As such it must be considered an emergency.
Risk factors
Immune-mediated thrombocytopenia (IMT) seems to affect mostly middle-aged dogs and might have a breed-related component as Poodles, Cocker spaniels, and English sheepdogs seem more predisposed to it.
Other symptoms might arise from other diseases associated with secondary IMT.
Possible causes
IMT can be either primary or secondary.
Primary IMT is uncommon and idiopathic, meaning that it appears spontaneously for unknown reasons. In the case of primary IMT, the immune system misidentifies platelets as a threat and destroys them.
How secondary IMT develops is still an object of research but it is associated with numerous conditions.
Recent vaccination may be linked to secondary IMT but a direct causal relationship has not been verified.
Main symptoms
IMT can sometimes be asymptomatic. When clinical signs arise they are mostly linked with abnormal bleeding and anemia.
Testing and diagnosis
The diagnostic process consists of bloodwork to evaluate the number of platelets in the blood. A definitive test to identify anti-platelet antibodies is not available yet, so the diagnosis of IMT is usually reached through the elimination of other possible causes of thrombocytopenia.
Other specific tests might be needed to address the possible underlying cause in cases of secondary IMT.
Steps to Recovery
Primary IMT is rare and it is often a consequence of another infectious, parasitic, or immune mediated disease.
Treatment focuses on controlling abnormal bleeding and suppressing the immune system to stop the destruction of platelets. The treatment is usually based on the prescription of corticosteroids, beginning with a high dosage and then tapering the therapy for up to 4 to 6 months. For the treatment to work it is also necessary to address the possible underlying condition.
During treatment supportive therapy is fundamental and includes cage rest (to avoid injuries and severe bleeding) and blood transfusions for patients showing signs of anemia.
The platelet count usually starts rising 7 to 10 days after starting treatment. Once the count is normalized, therapy is usually tapered down over several months.
The prognosis is generally good with a quick and effective treatment, with a survival rate of 70% to 90%.
Prevention
Primary IMT is idiopathic and cannot be prevented. Vaccinations and veterinary approved anti-parasitic products can be used to prevent associated conditions that can lead to secondary IMT, including distemper, leptospirosis, and heartworm disease.
IMT is not contagious in itself, some underlying conditions that might lead to secondary IMT are contagious.
Is Immune Mediated Thrombocytopenia in Dogs common?
Primary IMT is rare in dogs.
Secondary IMT is much more common than primary IMT.
Typical Treatment
- Corticosteroid therapy throughout 4 to 6 months
- Supportive care
- Blood transfusions
- Treatment for underlying conditions
