Thrombocytopenia in dogs is defined as a reduced levels of circulating thrombocytes (platelets) below the normal cut-off value of 2 x 1011/L.
Thrombocytopenia may result from reduced platelet production, increased platelet sequestration, increased platelet utilization or destruction. Consumptive coagulopathies represent the most common cause of increased platelet utilization, whereas immune-mediated thrombocytopenia, either primary or secondary, is the most common cause of increased platelet destruction.
Causes of canine thrombocytopenia include:
- - Dirofilaria immitis, Angiostrongylus vasorum, Rickettsia spp, Leishmania infantum, Ehrlichia canis, Borrelia burgdorferi, Babesia rossi, Anaplasma phagocytophilum
- Neoplasia, splenic torsion
- Immune-mediated diseases - e.g. immune-mediated thrombocytopenia, immune-mediated neutropenia, immune-mediated hemolytic anemia, lupus erythematosus
- Recent drug therapy - potentiated sulfonamides
- Live vaccination administration - this relationship not definitively established in dogs
- May-Hegglin anomaly
- Cutaneous-renal vasculopathy
Clinical symptoms associated with this condition include lethargy, fever, melena, hematemesis, hematuria, hematochezia, epistaxis and mucosal petechiations or ecchymotic hemorrhages on the mucous membranes. Many of these symptoms are referable to underlying thromboembolism and/or hemorrhagic episodes. Spontaneous hemorrhage does not typically occur unless platelets are less than 50,000 and some dogs, buccal mucosal bleeding times may be normal.
Diagnosis is one of exclusion of underlying cause and treatment should be directed at addressing the underlying disease state which should be accurately assessed in order to maximize clinical response and survival.
Initial therapy is aimed at ameliorating the coagulopathy with use of intravenous fresh frozen plasma to replace lost thrombocytes and use of glucocorticoids at an immunosuppressive dose, cyclosporine, busulfan or azathioprine.
The use of adjunct therapies such as lithium carbonate or human intravenous immunoglobulin have significantly reduced recovery times in some dogs and should be considered where financial constraints are not problematic.
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