|Mutation:||chr2:19371988-19371989: 236 bp insertion; chr2:19371976-19371988: 13 bp duplication (dup CACACAAAGGTTT)|
|Breed(s):||Carlin Pinscher, Miniature Pinscher|
Cystinuria (miniature pinscher type) is an inherited disease affecting kidney function in dogs. The SLC7A9 gene codes for a protein that allows the kidneys to transport cysteine and other amino acids from the urine. Normal kidneys reabsorb the Amino Acid cystine so that only small amounts pass into the urine, while dogs with mutations of both copies of the SLC7A9 gene fail to reabsorb cystine allowing high amounts to pass into the urine, hence the name cystinuria. Cystine can form crystals and/or stones in the urinary tract which can block the ureters or Urethra and stop the normal flow of urine. Affected male dogs present with symptoms related to cysteine bladder stones around one year of age, however female dogs tend to develop symptoms later than males. Symptoms of disease include straining to urinate, frequent urination of small volumes or inability to urinate. In miniature pinschers, males and females are equally affected with excess cysteine in the urine, but obstruction of urine flow is more common in males due to differences in anatomy. Dogs with cystinuria often have recurrent inflammation of the urinary tract and if not treated, urinary stones can cause urinary tract infections, kidney failure and even death.
Genetic testing of the SLC7A9 gene will reliably determine whether a dog is a genetic Carrier of cystinuria (miniature pinscher type). Cystinuria (miniature pinscher type) is inherited in an Autosomal Dominant manner in dogs meaning that they only need to inherit one copy of the mutated gene from a parent to develop the disease. Dogs identified to have the genetic Mutation are expected to have features of the disease, though symptoms can be very mild and dogs may appear healthy. Each pup that is born to a single affected parent has a 50% chance of inheriting one copy of the SLC7A9 gene mutation and having the disease. If both parents are affected, the chance of having affected offspring increases to 75-100%. 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 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.
- Brons AK, Henthorn PS, Raj K, Fitzgerald CA, Liu J, Sewell AC, Giger U. SLC3A1 and SLC7A9 mutations in autosomal recessive and dominant canine cystinuria: A new classification system. J Vet Intern Med. 2013 Nov;27(6):1400-8. [PubMed: 24001348]