Signs of IMT
Patients with IMT typically present with petechiae (pinpoint hemorrhage), ecchymosis (bruising) or overt hemorrhage (e.g.,
epistaxis, gingival and intestinal bleeding, prolonged bleeding after injury). Patients may appear clinically normal, or they
may be presented as emergencies because of anemia or as a result of bleeding into hollow cavities (e.g., hemothorax, hemoabdomen).
Consider these diagnostic tests if you suspect a patient has IMT: an accurate platelet count, a coagulation profile (e.g.,
activated clotting time, prothrombin time, partial thromboplastin time), a buccal mucosal bleeding time (to help rule out
a platelet function disorder) and a von Willebrand antigen test.
In the case of secondary thrombocytopenia, the ideal treatment is to control or eliminate the underlying cause. However, in
cases of idiopathic IMT, one or more immunosuppressants are typically used. In some patients with idiopathic IMT, an initial
intravenous dose of vincristine or vinblastine may be given. Corticosteroids—specifically prednisolone—are the backbone of
immunosuppressive therapy but are associated with a wide range of side effects.
Other drugs are often added for additional immunosuppression in refractory cases and to allow a more rapid taper of the corticosteroids.
Table 2 lists some of the more commonly used immunosuppressants used to treat IMT. Use of prednisolone is preferred over prednisone.
Prednisolone is the active metabolite of prednisone (does not require conversion by the liver), is more readily absorbed and
has more in vivo activity. In fact, some dogs are unable to develop therapeutic serum concentrations of prednisolone when
given prednisone.2 This may explain why some patients seem to respond poorly to immunosuppression with prednisone.
Table 2: Immunosuppressants used to treat IMT
If immunosuppression fails to control the IMT, consider splenectomy. Some case reports in the human literature have also described
the use of oral melatonin in cases of refractory IMT.3
Dr. Lyman is a graduate of The Ohio State University College of Veterinary Medicine. He completed a formal internship at the
Animal Medical Center in New York City. Lyman is a co-author of chapters in the 2000 editions of Kirk's Current Veterinary Therapy XIII and Quick Reference to Veterinary Medicine.
Dr. Runde is a graduate of the University of Pennsylvania School of Veterinary Medicine. He completed an internship at Hollywood
Animal Hospital. He is an associate veterinarian at the Animal Emergency and Referral Center in Ft. Pierce, Fla.
1. Huang AA, Moore GE, Scott-Moncrieff JC. Idiopathic immune-mediated thrombocytopenia and recent vaccination in dogs. J Vet Intern Med 2012;26(1):142-148.
2. Boothe DM. Small animal clinical pharmacology and therapeutics. 2nd ed. St. Louis, Mo: Elsevier Saunders, 2012.
3. Todisco M, Rossi N. Melatonin for refractory idiopathic thrombocytopenic purpura: a report of 3 cases. Am J Ther 2002;9(6):524-526.