Hereditary Nephritis (Samoyed Type)

Other Names: Alport syndrome, Samoyed hereditary glomerulopathy, X-linked nephritis, AS, HN, XLHN
Affected Genes: COL4A5
Inheritance: X-Linked Recessive
Mutation: Point Mutation
Breed(s): Samoyed

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Common Symptoms

Hereditary nephritis (samoyed type) is an inherited disorder of the kidneys affecting dogs. Normally protein is not present in the urine, but in affected dogs there is a defect that allows protein from the blood to be filtered by the kidneys and lost in the urine. Abnormal amounts of protein can be detected in the urine between two and three months of age at which time both affected male and Carrier female puppies are noted to be smaller and thinner than their unaffected littermates. Affected dogs begin showing signs of chronic kidney failure between 7 and 15 months of age. Symptoms of chronic kidney disease include excessive thirst and urination, vomiting, inappetence, weight loss, weakness and fatigue. If drinking excessively, some dogs may also inappropriately urinate in the house or in a crate. Due to its X-Linked Inheritance, male dogs are more frequently affected with this disease than female dogs. Female dogs which carry this Mutation can also show signs of kidney disease however, disease progression in females is generally slower with some dogs showing minimal to no signs of kidney disease. Affected male dogs eventually die of chronic kidney failure by 15 months of age.


Testing Tips

Genetic testing of the COL4A5 gene will reliably determine whether a dog is a genetic Carrier or affected with hereditary nephritis (samoyed type). Hereditary nephritis (samoyed type) is inherited in an X-Linked Recessive manner in dogs meaning that female dogs typically must receive two copies of the mutated gene (one from each parent) to develop the disease while male dogs only require one copy of the mutated gene from the mother in order to develop disease. Therefore, male dogs more commonly present with symptoms of the disease. Although much less common, carrier female dogs may present with mild symptoms though with slower disease progression than male dogs. Each male pup that is born to a female dog known to be a carrier of hereditary nephritis has a 50% chance of inheriting the disease. Female dogs that are not carriers of this Mutation have no increased risk of having affected pups. Reliable genetic testing is important for determining breeding practices. Because female carriers may have mild or no features of the disease, genetic testing should be performed before breeding. 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.


References

  • Baumal R, Thorner P, Valli VEO, McInnes R, Marrano P, Jacobs R, Binnington A, Bloedow AG. Renal disease in carrier female dogs with x-linked hereditary nephritis. Am J Pathol. 1991 Oct;139(4):751-64. [PubMed: 1928300]
  • Jansen B, Valli VE, Thorner P, Baumal R, Lumsden JH. Samoyed glomerulopathy: serial, clinical and laboratory (urine, serum biochemistry and hematology) studies. Can J Vet Res. 1987 Jul;51(3):387-93. [PubMed: 3651895]
  • Zheng K, Thorner PS, Marrano P, Baumal R, McInnes RR. Canine X chromosome-linked hereditary nephritis: A genetic model for human X-linked hereditary nephritis resulting from a single base mutation in the gene encoding the alpha-5 chain of collagen type IV. Proc Natl Acad Sci USA. 1994 Apr 26;91(9):3989-9. [PubMed: 8171024]