Immune Mediated Thrombocytopenia (IMT) is a serious disease in which the body’s immune system destroys the platelets in the blood. The name of this disease is a bit complicated but if we take each word by itself, it becomes more understandable. Immune Mediated means that the body’s own immune system is at the root or cause of the disease. Thrombocytopenia means inadequate numbers of platelets (thrombocytes) in the blood.
The causes for development of IMT are many and they all relate to factors that cause the immune system to be tricked into thinking that the platelets are no longer part of the body. The immune system suddenly sees the platelet as a foreign element and proceeds to destroy it, much in the same way it would destroy a bacteria or virus. We know that certain drugs (particularly antibiotics containing sulfur); vaccines, viral infections, bacterial infections, cancer and others have all been related to the development of IMT. Why one patient gets IMT while another does not is still a mystery.
Causes and Consequences of IMT:
Platelets are blood elements that are responsible for blood clotting. When a blood vessel is torn or broken, the platelets clog up the hole while it is repaired. Normally there are over 200,000 platelets in each milliliter of blood. If the number of platelets reduce below 80,000, there is the potential for spontaneous bleeding. Bleeding can be visible to the owner at the gums, from the nose, in the urine or feces. Or, it can occur internally in the brain, heart, kidneys, lungs or joints etc. and cause pain, rapid deterioration and even death.
While the platelets are being destroyed, there is an inflammatory response which will often lead to fever, inappetence, and malaise.
Diagnosis of IMT by Our Veterinarians:
Any bleeding pet has to be suspected of having IMT. Often times, the diagnosis is made as a result of low platelets found on a routine blood screen. Typically other reasons for bleeding must be ruled out using a coagulation profile and an immune panel is helpful in determining if there are abberations in the immune system.
Goals of Therapy and Treatment of Our Veterinary Clinic:
Treatment for IMT involves the following:
- Trying to determine and eliminate the causal factor (remove drugs, treat infections, remove cancer etc).
- Suppress the immune system’s activity to stop the destruction.
- Replace platelets if the count is dangerously low, or if there is evidence of spontaneous bleeding.
The first drug we use is Prednisone (a form of cortisone). Given at high doses, this drug will inhibit the immune system’s ability to kill the red cells. Often times, we must add additional drugs such as Vincristine, Cyclophosphamide, Azathiaprine or Cyclosporine, all of which are very potent drugs. All of these drugs have side effects that are fairly common. In general, the positive, life saving effects of the drugs outweigh the negative side effects, however, these patients must be monitored carefully both at home and with laboratory tests.
For patients that are severely thrombocytopenia (lack of platelets), transfusions may be necessary to provide platelets until their body can produce more. Transfusions can be life saving, but they do pose some risk of adverse reaction where the body rejects the new cells.
Because prednisone can cause stomach ulcers, we typically administer drugs to help protect the stomach during the course of treatment.
Prognosis for Alta Loma, Rancho Cucamonga, Upland, Ontario, Claremont, Fontana and the Inland Empire Communities:
It is important to understand that our treatment may not cure the disease, but instead, may keep it in remission. Most pets require treatment for a minimum of 6 months during which time we try to wean them slowly off the life saving drugs. In some cases, drugs are not enough to control the disease and we may have to surgically remove the spleen because this organ is the site where the majority of the platelet destruction takes place. Overall, 75% of pets with IMT can go on to live a normal life. Unfortunately, some patients will die from this disease despite even the most aggressive treatment. It is difficult to predict who will survive and who will succumb to the disease, but a positive response to initial therapy makes for a better prognosis than a pet that does not respond initially. Each time a pet comes out of remission (the platelet count drops again) the prognosis gets more guarded.