Clotting Disorders of the Platelets in Dogs

Thrombocytopathies in Dogs

Thrombocytopathies are defined as disorders of the blood platelet and abnormal functioning of the platelets. Thrombocytopathic animals are those which typically have normal platelet counts on examination, but have spontaneous or excessive bleeding due to a failure of the platelets to bind to each other, or clot normally. Bleeding from the mucous membranes – nose, mouth ears, anus – is the most common sign. Thrombocytopathies may first become apparent in young animals when excessive bleeding occurs with the loss of baby teeth.

Thrombocytopathies can be acquired or hereditary; they affect the main functions of platelets: activation, adhesion and aggregation. That is, they lack the ability to group together and adhere to each other, an important function for sealing wounds. This can result in severe bleeding from even the smallest wound. Animals having a low blood platelet count with concurrent thrombocytopathia will bleed more excessively than expected for the existent platelet count. Any breed of dog can be affected by acquired thrombocytopathies, but some breeds may be more prone to certain types (see Symptoms and Causes, below).

Symptoms and Types

• Spontaneous bleeding
• Nosebleeds (epistaxis)
• Bleeding is often from mucosal surfaces (nose, mouth, gums, etc.)
• Basset hounds with hereditary thrombopathia develop auricular hematomas (blood build-up in the ear flap)
• Prolonged bleeding in some animals during diagnostic or surgical procedures

Causes

Acquired thrombocytopathy

• May occur in response to some drugs
  • Painkillers (e.g., aspirin), anesthetics
  • Antibiotics
  • Nonesteroidal anti-inflammatory drugs
• Secondary to systemic disease
  • Kidney disease
  • Inflammation of the pancreas
  • Liver disease
  • Parasitic disease
  • Cancer

Hereditary thrombocytopathy

• von Willebrand disease
• Basset hound hereditary thrombopathia and Spitz thrombopathy
• Aggregation (platelet clumping) defect – otter hounds and great Pyrenees with type I Glanzmann thromboasthenia
• Gray collies with cyclic hematopoiesis (red blood cell production) and Chediak-Higashi syndrome
• Some American cocker spaniels

Diagnosis

Your veterinarian will perform a complete physical exam on your dog after taking a full medical and background history, and a description of the onset of symptoms from you. Your veterinarian will order a biochemical profile, a complete blood count, a urinalysis and an electrolyte panel. The complete blood count may show a condition of anemia if bleeding has been severe.  Platelet counts are often normal in dogs with inherited thrombocytopathies, but low counts are sometimes seen in otter hounds.

A von Willebrand disease assay can be performed in animals suspected of having this disease. Platelet function testing can also be done in select laboratories. Coagulation tests (prothrombin time [PT] and activated partial thromboplastin time [APTT]) should be ordered to eliminate coagulopathy (a disease affecting the blood’s ability to clot) as a cause of the excessive bleeding.

Mucosal bleeding time can be measured by making a small incision on the inside of the cheek (buccal) in the mouth. The amount of blood and length of time it takes for the incision to be sealed with a clot of blood will either confirm or rule out a clotting disorder.