It is a haemophilia-like disease, typified by the reduced quantity or absence of a certain clotting factor in the plasma. The factor is a glycoprotein and is necessary for the normal platelet function of blood clotting.
 
It should be noted that vWD is not a death sentence for dogs, in fact many dogs with the disease can live quite normal lives and show no complications e.g. carriers of the recessive form who do not have the disease - Affected who do not have bleeding episodes. With careful mating strategies and genetic screening, the breeder can begin to bring the percentage of carriers or affected in their pedigree down and make an impact on the levels seen in different breeds.
 
 Readings for vWD are as follows:

 
CLEAR  
 no presence of the disease gene and cannot pass on any disease gene.
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  CARRIER
  One copy of the disease gene is present, however the animal does not exhibit any symptoms of the disease. Therefore no medical problems arise. Carriers will pass on the disease gene to 50% of their offspring.
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AFFECTED
  Two copies of the disease gene are present. The animal will always pass on the disease gene (mutation) to its offspring.
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See Tables Below For Mating Results