Immune Mediated Thrombocytopenia in Cats

IMT is a form of thrombocytopenia (low platelets) that occurs in cats when the immune system begins to destroy platelets within the body.

Platelets (also known as thrombocytes) are a cell within the bloodstream that assist with clotting. When the loss is severe, this can lead to delayed blood clotting, bruising, and spontaneous bleeding.

IMT is rare, but potentially life threatening. With prompt diagnosis and treatment, prognosis of IMT is generally good, but a delay in diagnosis may become life threatening with a poor prognosis.

Cats with clinical signs consistent with IMT require urgent veterinary care.

Other symptoms of IMT stem from abnormal bleeding.

Symptoms may vary in severity if prolonged bleeding occurs. Some symptoms can cause severe secondary symptoms. For example, bleeding into the eyes can cause blindness, whereas bleeding into the brain can cause seizures.

There are two forms of IMT.

• Primary ITM (also known as idiopathic immune-mediated thrombocytopenia) is when a cause cannot be determined
• Secondary IMT occurs due to an underlying condition such as cancer, viral disease (such as feline leukemia virus), or drug administration (such as antibiotics or chemotherapy agents).

Recent vaccination has been suspected as a potential cause for IMT, but this has not yet been established.

A diagnosis of IMT begins with a thorough physical examination, where bruising or petechiae may be observed.

Often, diagnosing IMT is done by a process of exclusion. There are many different conditions that may cause a low platelet count and similar symptoms, such as neoplasia, inflammatory disease, bone marrow disease.

Tests to assist with diagnosis include:

• Bloodwork
• Coagulation time tests
• Bone marrow biopsy

Treatment of IMT focuses on controlling any bleeding, reducing the risk of injury (cage rest or decreasing exercise), suppressing the immune system to stop destruction of platelets (by using immunosuppressive medications), and in the case of secondary IMT, treating any underlying causes. Blood or platelet transfusions may assist in treatment, but they are often short lived if the body is continuing to destroy platelets.

Without treatment, IMT does not go away and only worsens with time. The prognosis of IMT varies from good to guarded, and often depends on where bleeding has occurred and speed of diagnosis. Risk of death is much higher in cases of bleeding into vital organs such as the kidneys, brain, and digestive tract. Even with treatment, there is a chance of relapse. Often, a recurrence of IMT has a much more guarded prognosis.

There is no way to truly prevent development of IMT. However, many veterinarians chose to reduce or eliminate future vaccinations in cats that have been previously diagnosed and treated, though a relationship between the two has not yet been established.

IMT is not a contagious condition.

IMT is a rare condition in cats.

• Immunosuppressive medication
• Supportive care (cage rest, exercise reduction)
• Immunoglobulin or platelet transfusions

Treatment of IMT can be a long process, often taking upwards of 6 months to taper immunosuppressive medication.