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Thrombopathia Basset Hound Type (TBP)
| Acronym: | TBP, TRB |
| Gene: | RASGRP2 |
| Mutation: | c.509_511del |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Thrombopathia Basset Hound type is an inherited bleeding disorder affecting the Basset Hound breed. Thrombopathia in Basset Hound has been for the first time reported in 1979 as a bleeding disorder associated with abnormal platelet function. Research has continued, and detailed research about this defect started in 1981. Also, other bleeding disorders have been documented in this breed, such as von Willebrand’s syndrome and hemophilia. Platelets, or thrombocytes, have a key role in bleeding prevention through the clumping of blood vessel injuries. At a site of vascular injury, platelets are exposed to the surface which is not from a blood vessel, and they initiate to aggregate with each other, which results in the formation of a hemostatic plug that will seal the defect. In the formation of this plug, fibrin has a role as its stabilizer.
Excessive bleeding disorders in dogs, or canine hemorrhagia, can be divided into two groups: intrinsic, inherent platelet defects, in which the platelet itself is abnormal and extrinsic, external defects, where the abnormality underlies some factor necessary for normal platelet function. Like this, the most known canine extrinsic platelet defect is recognized in von Willebrand’s syndrome, while intrinsic platelet defects are less commonly recognized. Thrombopathia Basset Hound Type is an inherent platelet defects type hemorrhagia. Due to defects within the platelets, they are unable to form a blood clot. The defect in the platelets of the basset hounds is suspected to be related to a structural or functional deficiency of specific surface glycoprotein receptors, similar as has been reported in humans with Glanzmann’s disease and Bernard-Soulier syndrome, human bleeding disorders.
Thrombopathia Basset Hound type is characterized by cutaneous and mucosal bleeding and prolonged bleeding time, as a consequence of abnormal platelet function. The bleeding severity can vary, from mild to severe. However, platelets in affected Basset Hounds appear normal-sized. Some signs of disease can be recognized by the owner. When a puppy’s teeth are shed, excessive bleeding can occur. Also, small pinpoints that appear and disappear easily can be seen on the dog’s abdomen, as a symptom of capillary bleeding in the skin. Bleeding on the tips of the ear, around the gums, and nasal bleeding can appear. As the disorder can vary in its severity, dogs with a mild form of the disorder may not exhibit any of these signs and have no or only minor bleeding post-operation, due to a sufficient level of normal functioning platelets.
Thrombopathia Basset Hound type is caused by a mutation in the RASGRP1 gene. The frequency of the mutation is unknown. The disorder is inherited in an autosomal recessive manner. Healthy parents of an affected puppy are obligate heterozygotes and therefore carry one mutant allele. Heterozygotes have no symptoms. Dogs homozygous for the mutation will display the symptoms of the Thrombopathia Basset Hound type. At conception, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Johnstone IB, Lotz F: An inherited platelet function defect in Basset hounds. Can Vet J 20:211-215, 1979.
Mattson, J. C., Estry, D. W., Bell, T. G., & Patterson, W. R. (1986). Defective contact activation of platelets from dogs with basset hound hereditary thrombopathy. Thrombosis Research, 44(1), 23-38.