Thrombopathia (Newfoundland type) is an inherited bleeding disorder affecting dogs. Affected dogs have abnormal platelet function. In thrombopathia (Newfoundland type), Platelets are unable to stick properly to one another and therefore cannot clot normally. The risk for excessive and spontaneous bleeding can range from mild to severe. The most common symptoms in affected dogs are recurrent nose bleeds and excessive bleeding of the gums when a dog sheds its teeth or chews on hard objects. Affected dogs can also bruise easily, get blood filled masses (hematomas) under their skin and within muscles with mild trauma. They can have internal bleeding and bloody or dark tarry feces. Dogs may show signs of lameness or stiffness if bleeding in the joints is present. Although dogs with this disorder are at risk for spontaneous Hemorrhage and internal bleeding, affected dogs may not be identified until a surgery is performed or trauma occurs at which time excessive bleeding is noted. Veterinarians performing surgery on known affected dogs should have ready access to blood banked for transfusions. Dogs can have a normal lifespan with this condition although they are susceptible to life-threatening bleeding with an accidental injury or any surgical procedure.
Genetic testing of the RASGRP1 gene will reliably determine whether a dog is a genetic Carrier of thrombopathia (Newfoundland type). Thrombopathia (Newfoundland type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of being a carrier of the RASGRP1 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Boudreaux MK, Catalfamo JL, Klok M. Calcium-diacylglycerol guanine nucleotide exchange factor I gene mutations associated with loss of function in canine platelets. Transl Res. 2007 Aug; 150(2):81-92.