Veterinary Medicine - August 2007 - (Page 536)

Immune-mediated thrombocytopenia O P E E R - R E V I E W E D tomy, intravenous gamma globulin administration, plasmapheresis, or treatment with danazol. Management of immune-mediated thrombocytopenia by splenectomy has not been thoroughly investigated in a large number of dogs, and published success rates are highly variable. 2,8 Blood smears and PCR testing should be done to monitor for Mycoplasma immune-mediated thrombocytopenia.6,8 It may take three to six months to reach peak effect. Once the prednisone has been reduced to alternate-day dosing, the danazol dose is gradually tapered to the minimum effective dose.8 A small number of dogs with refractory immune-mediated thrombocytopenia have responded to danazol.27 Liver enzyme activities should be mon- separate times. Monitoring the platelet count before and for a few weeks after vaccination is warranted. SUMMARY Immune-mediated thrombocytopenia is a common acquired coagulation disorder in dogs resulting from antibody-mediated clearance of platelets though the mononuclear phagocytic system. It is mainly a diagnosis of exclusion. Primary immune-mediated thrombocytopenia is confirmed by ruling out secondary disorders that can mediate platelet destruction by the immune system. Primary immune-mediated thrombocytopenia is treated with immunosuppressive therapies, whereas secondary immune-mediated thrombocytopenia is treated by addressing the underlying disorder, often with concurrent immunosuppressive therapy. The prognosis for this disorder is guarded to good. If dogs with primary immune-mediated thrombocytopenia fail to respond, additional immunosuppressive therapy may be required, although reevaluation for an underlying cause that was not identified initially should also be considered. O REFERENCES 1. Mackin A. Canine immune-mediated thrombocytopenia: Part I. Compend Contin Educ Pract Vet 1995;17:353-362. 2. Lewis DC, Meyers KM. Canine idiopathic thrombocytopenic purpura. J Vet Intern Med 1996;10:207-218. 3. Scott MA. Immune-mediated thrombocytopenia. In: Kristensen AT, ed. Schalm’s veterinary hematology. 5th ed. Baltimore, Md: Lippincott Williams & Wilkins, 2000;478-486. 4. Topper MJ, Welles EG. Hemostasis. In: Latimer KS, Mahaffey, EA, Prasse KW, eds. Veterinary laboratory medicine: clinical pathology. 4th ed. Ames: Iowa State University Press, 2003;99-135. 5. Boudreaux MK. Platelets and coagulation. An update. Vet Clin North Am Small Anim Pract 1996;26:1065-1087. 6. Grindem CB. Infectious and immune-mediated thrombocytopenia. In: Bonagura JD, ed. Kirk’s current veterinary therapy XIII small animal practice. Philadelphia, Pa: WB Saunders Co, 2000;438-442. 7. Breitschwerdt EB. Infectious thrombocytopenia in dogs. Compend Contin Educ Pract Vet 1988;10:1177-1191. 8. Mackin A. Canine immune-mediated thrombocytopenia: Part II. Compend Contin Educ Pract Vet 1995;17:515-534. 9. Chisholm-Chait A. Mechanisms of thrombocytopenia in dogs with cancer. Compend Contin Educ Pract Vet 2000;22:1006-1018. 10. Terrazzano G, Cortese L, Piantedosi D, et al. Presence of antiplatelet IgM and IgG antibodies in dogs naturally infected by Leishmania infantum. Vet Immunol Immunopathol 2006;110:331-337. 11. Lewis DC, Bruyette DS, Kellerman DL, et al. Thrombocytopenia in dogs with anticoagulant rodenticide-induced hemorrhage: eight cases (1990-1995). J Am Anim Hosp Assoc 1997;33:417-422. 12. Cowan SM, Bartges JW, Gompf RE, et al. Giant platelet disorder in the Cavalier King Charles Spaniel. Exp Hematol 2004;32:344-350. 13. Cohn LA. Immune-mediated blood dyscrasias: clinical Initially, monitor the platelet count every one to two weeks for the first two months. haemocanis (formerly Haemobartonella canis) and Babesia canis before and for several weeks after splenectomy.8 Immune-mediated thrombocytopenia can persist after the splenectomy through the actions of the hepatic mononuclear phagocytic system.8 Intravenous gamma globulins are given as a single infusion and are thought to competitively bind to macrophage receptors, decreasing platelet clearance by the mononuclear phagocytic system. But the effect is transient and this treatment is generally cost-prohibitive.8 In a recent report, human intravenous immunoglobulin was used at a dose of 0.28 to 0.76 g/kg intravenously.25 Other published doses for human intravenous immunoglobulin have ranged from 0.5 to 1.5 g/kg.26 Plasmapheresis is expensive and technically difficult, and its availability is limited in veterinary patients.8 Danazol (5 to 10 mg/kg orally every 12 hours) is an androgen that may decrease production of antiplatelet antibodies and decrease macrophage receptors, impairing mononuclear phagocytic system clearance of platelets.2,8 It is used concurrently with prednisone for managing itored monthly. Danazol’s expense may preclude its use in large-breed dogs.8 Monitoring Initially, monitor the platelet count every one to two weeks for the first two months. After that, recheck the count before and after any reduction in drug dose. For patients in complete remission, recheck the platelet count at three-month intervals. Monitoring the platelet count is critical because clinical signs of thrombocytopenia do not become evident until platelet numbers are severely decreased.8 VACCINATION IN AFFECTED DOGS In patients in which immune-mediated thrombocytopenia is suspected to be secondary to vaccine administration, avoid the potentially causative vaccine or vaccines in the future. Administering distemper-hepatitis vaccines may lower platelet counts, with the peak effect one week after vaccination, so vaccination should be avoided in thrombocytopenic patients.28 For patients that have recovered from immune-mediated thrombocytopenia, we recommend administering only core vaccines and administering the vaccines at 536 August 2007 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - August 2007

Contents A Veterinary Medicine Interview Veterinary Voices Idea Exchange Diagnosis and Treatment of Solar Dermatitis in Dogs Diagnostic Imaging for Linear Foreign Bodies in Cats Overcoming the Diagnostic and Therapeutic Challenges of Canine Immune-Mediated Thrombocytopenia Ophthalmic drugs: What’s new? CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - August 2007

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