Platelet dysfunction (thrombocytopathia, Basset hound thrombopathia)

What is ... ?: 

 These are disorders of small blood cells called platelets or thrombocytes. Platelets play an important role at several stages of the body's response to any injury that causes bleeding. One function of platelets is to aggregate or "clump" at the site of blood vessel injury to form an initial plug. Platelets also facilitate blood clotting, in conjunction with the clotting factors, and release substances active in inflammation and tissue repair. With these disorders, platelets do not respond normally to the activation signals that occur following injury to a blood vessel.  Affected dogs are therefore more susceptible to bruising and hemorrhage.

 Disorder Abnormality Breeds affected Special tests
Basset thrombopathia (disorder of signal transduction)

 Platelets fail to aggregate and secrete granules in response to normal stimuli

  Basset hound, Finnish spitz  abnormal platelet adhesion and aggregation, normal clot retraction
Thrombasthenia membrane glycoprotein disorder; reduction or absence of membrane proteins necessary for normal platelet function Otterhound, Great Pyrenees  abnormal adhesion and clot retraction, aggregation failure, reduced or absent GPIIb/IIIa
 Storage pool defect  defect in secretory granules American cocker spaniel abnormal aggregation, normal clot retraction, abnormal  ADP secretion and storage
 Platelet procoagulant deficiency   German shepherd  normal aggregation and secretion, normal clot retraction, abnormal prothrombinase activity
 Complex or undefined    Collie, boxer  abnormal platelet function
How is ... inherited?: 

These traits are autosomal, with recessive or unknown expression.

What does ... mean to your dog & you?: 

 Some dogs have only a mild bleeding tendency which is fairly easily controlled. With dogs who are prone to more severe bleeding, owners will need to be particularly attentive to catch small injuries and attend to them, and seek veterinary attention if necessary.
 
In affected dogs, it is best to consult your veterinarian before using any over-the-counter medications. For example, drugs such as aspirin alter the function of platelets, and should be avoided in dogs with bleeding disorders.

How is ... diagnosed?: 

 Generally these dogs are brought to the veterinarian at a young age when the owner notices unusual bleeding. This can be in the form of nose bleeds, blood in the urine or stool, or small hemorrhages or bruising in the skin, ears, mouth or retina of the eye. There may also be prolonged bleeding in response to a small injury. Where the bleeding tendency is mild, the condition may only be suspected when your dog first undergoes surgery.
 
Your veterinarian will do blood tests to determine the cause of the abnormal bleeding. With this condition, platelet numbers are normal but those tests that measure platelet function will have abnormal results.

For the veterinarian: Mucosal bleeding time is prolonged. Platelet numbers and blood coagulation parameters are generally normal. Platelet function testing for classification of hereditary defects may require referral (clot retraction, platelet aggregation and secretion studies, flow cytometry). Platelet dysfunction should be considered in any young dog with abnormal bleeding when more common disorders (von Willebrand's, thrombocytopenia, coagulopathies) have been ruled out.

How is ... treated?: 

This condition cannot be cured but it can be managed, depending on the severity. Your veterinarian will discuss this with you when the diagnosis is made. You may be able to control mild bleeding by applying prolonged pressure. In other circumstances, sutures may be required. Severe bleeding will require transfusion of fresh platelets, either in the form of fresh whole blood or platelet-rich plasma. If your dog requires surgery, your veterinarian may recommend a transfusion pre-operatively as a precaution, depending on the severity of your dog's thrombopathia and the type of surgery.

Breeding advice: 

Affected dogs, their parents (who are carriers), and their siblings (approximateley 50% of whom will be carriers) should not be used for breeding.The trait for thrombasthenic thrombopathia has been largely eliminated from the otterhound population through selective breeding.

Resources: 

Brooks MB, Catalfamo JL. Platelet dysfunction. In: Bonagura JD, Twedt DC, eds. Kirk's Current Veterinary Therapy XIV. Missouri: Saunders Elsevier, 2009:292-297.
Brooks MB.  Platelet dysfunction. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:66-68.


What breeds are affected by ... ?
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