Cystinuria Type B variant 3

 

Gene: SLC7A9

Transmission: Most likely autosomal, recessive (still to be verified).

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation:  Substitution, gene SLC7A9; c.881 T>A, p.(Val294Glu), exon 7, feline chromosome E2.

Medical systems: metabolic, renal

Breed: Maine Coon, Siamese, Siberian, Sphynx

Age of onset of symptoms: Variable, between 4 months and 12.2 years, with an average age of 3.6 years.

Cystinuria type B is a genetic disease that primarily affects the urinary system. It is caused by a metabolic abnormality in the cells of the proximal renal tubule affecting the transport and reabsorption of the amino acids cystine, ornithine, lysine and arginine.  This blockage of resorption can lead to the formation of uroliths (cystine stones in the urinary tract) and urinary obstruction.  The main clinical signs observed include a frequent urge to urinate or difficulty in urinating as well as blood in the urine.  The cat may position itself in the litter box to urinate but fail to do so, complaining and circling. The cat may also have significant pain during urination, which may cause listlessness or vomiting. If the disease progresses, it can cause destruction of the kidneys resulting in kidney failure.  Complete blockage can result in bladder rupture.  Symptoms and severity depend on the size and location of the stones formed and treatment may include medical interventions, surgery, or dietary changes.  A DNA test for the mutation is available.  In general, cystinuria is less common in cats than in dogs.

 

References:

OMIA link: [2023-9685]

Anderson H, Davison S, Lytle KM, et.al. (2022) Genetic epidemiology of blood type, disease and trait variants, and genome-wide genetic diversity in over 11,000 domestic cats.  PLoS Genet. 16;18(6):e1009804.  [pubmed/35709088]

Kovaříková S, Maršálek P, Vrbová K, Scarpa P. (2021) Cystinuria in dogs and cats: what do we know after almost 200 years? Animals (Basel) 11:2437.  [pubmed/34438894]

Mizukami K, Raj K, Osborne C, Giger U. (2016). Cystinuria associated with different SLC7A9 gene variants in the cat. Plos One 11:e0159247.  [pubmed/27404572]

 

Contributed by : Claudia Lachapelle, Class of 2027, Faculté de médecine vétérinaire, Université de Montréal.   (Translation DWS).