Canine idiopathic thrombocytopenia (CIT), also called immune mediated thrombocytopenia (ITP), is a type of hematologic disease characterized by an abnormally low number of thrombocytes resulting from the destruction of the blood cells by a dog's own immune system. Thrombocytopenia may be congenital or acquired. The condition is sometimes associated with abnormal bleeding under the skin or from the gums. Females and small breeds of dogs appear predisposed to immune-mediated thrombocytopenia. Most affected dogs are middle-aged or spayed females. Cocker spaniels, poodles, and English sheepdogs are considered to predisposed to this disease.4
Numerous factors are involved in the development of acquired thrombocytopenia. These include bone marrow malformations, transfer of maternal antibodies to the newborn, irradiation, and drugs. Drug sensitivity leading to thrombocytopenia may develop within a few days of initiation of drug therapy. Discontinuance of the offending drug is rapidly accompanied by return to the normal platelet levels. Other agents include toxins; viral, rickettsial and protozoan infections; chronic hepatitis; myelogenous leukemia; tumors (hemangiosarcoma); Addison disease; vitamin B12 or folate deficiencies; severe iron deficiency or immune-mediated disorders. Increased platelet destruction may also result from overly-active macrophages and other immune-mediated mechanisms. The most common infectious causes of thrombocytopenia in dogs is ehrlichiosis, canine hepatitis virus, and distemper virus.
Cocker spaniels are believed to be predisposed to canine idiopathic thrombocytopenia disease
Thrombocytopenia has also been associated with peritonitis, myasthenia gravis, immune-mediated hemolytic anemia, and disseminated intravascular coagulation disorder (DIC). DIC disorder develops when the dog's blood clotting mechanisms are activated throughout the body instead of being localized to an area of injury. As a result, the blood clotting factors are used up to such a degree that they are not available to form clots at sites of real tissue injury. Severe bleeding, whether acute or chronic, is unlikely to cause thrombocytopenia because of the extra platelets stored in the spleen and other sites. In mild cases, affected dog may become lethargis, weak and have nosebleeds. There are multiple pinpoint, purplish-red spots in the mucous membranes and skin due to internal bleeding. Dogs that are more severely affected may have blood in the urine and feces. The diagnosis of ITP is difficult. Treatment involves corticosteroids alone or in combination with other immunosuppressive drugs. Most dogs recover with single or multiple courses of treatment.
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- Mary Anna Thrall. Veterinary Hematology and Clinical Chemistry
- Nemi Chand Jain. Essentials of Veterinary Hematology
- Susan M. Cotter. Hematology
- Application of vincristine-loaded platelet therapy in three dogs with refractory immune-mediated thrombocytopenia