Cystinuria, type B

Cystinuria is an inherited metabolic disorder of amino acid transport in the kidneys. In affected individuals, cystine is accumulated in the urine, cystine crystals and urinary stones are formed. These irritate the urinary tract, causing urinary stagnation and increasing the susceptibility of the urinary tract to infection. Clinically, cystinuria is manifested by dark and distinctly foul-smelling urine with an admixture of blood. Urination is painful and often unsuccessful.

As in humans and dogs, the disease is genetically heterogeneous in cats. So far, three variants in the SLC7A9 gene have been found to cause this disease in cats. These are the missense mutations c.706G>A, c.1175C>T and c.881T>A, which have been identified in Maine Coon, Siamese and Siberian cats and in the Sphynx breed.

There are not enough data available to determine the mode of inheritance. Autosomal recessive or autosomal dominant inheritance is assumed. The genetic test can clearly reveal the genotype of an animal and is a useful tool for breeders to avoid unintentional breeding of affected individuals.

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References:

Mizukami, K., Raj, K., Osborne, C., Giger, U. : Cystinuria associated with different SLC7A9 gene variants in the cat. PLoS One 11:e0159247, 2016. Pubmed reference: 27404572.