When a dog’s platelet count goes below the normal range, a blood disorder called thrombocytopenia may be the reason. It can affect the platelets in four ways: decrease the population of platelets, sequester platelets (removal of platelets from where they normally should be present), and increase destruction or use of platelets.

Medications containing estrogen, antibiotics like cephalosporins, recent vaccinations, health issues like neoplasia or tumors and immune disorders can all cause a decrease in the population of platelets. In addition, an enlarged spleen or liver usually results in sequestration of platelets. Moreover, blood loss, vasculitis (inflammation disorders that destroy blood vessels), and disseminated intravascular coagulation, which leads to blood clot formation, can all increase the use of platelets. Furthermore, increased destruction of platelets is normally immune mediated and caused by certain medications, infectious diseases such as canine distemper, Rocky Mountain spotted fever, ehrlichiosis (caused by a parasite), and heartworm disease.  Certain auto immune can also destroy platelets.

Signs that a dog is suffering from thrombocytopenia are lethargy, weakness, collapse, pale mucus membranes, petechial (small red spots on the skin or mucus membranes caused by hemorrhage), hematuria (passing blood in urine), hemorrhage of the eye, gastrointestinal bleeding resulting in black tarry stool, bleeding from the nose, and sometimes neurologic signs may be present.

Since thrombocytopenia can be fatal if left untreated, a veterinarian should be contacted if the disease is suspected. A complete exam will be performed and blood work, such as a complete blood count, will be performed. A canine heartworm test may be recommended to rule out heartworm disease, serum titers to rule out ehrlichiosis and Rocky Mountain spotted fever, a coagulation panel to rule out clotting disorders, and ANA test to check for symmetrical lupus erythematosus, and Coombs’ test to rule out immune-mediated hemolytic anemia. A vet may also recommend radiographs and ultrasound imaging to rule out internal bleeding or neoplasia.

Depending on the severity of the bleeding disorder, certain medications can be prescribed like antibiotics, steroids, and other immunosuppressive medications. If the bleeding is severe, blood transfusions may be required.  Non-steroidal anti-inflammatories and aspirin should be avoided in dogs with bleeding disorders. Once identified and the bleeding is controlled, a dog affected with thrombocytopenia should be closely monitored as relapse could occur.