Xanthinuria II in Dachshunds

Xantinuria is a hereditary disease characterized by the excretion of large amounts of xanthine in the urine. The enzyme that converts xanthine to uric acid is damaged. Xanthine is a product with low solubility, precipitates easily and forms xanthine stones. These concretions act like most uroliths - they irritate the urinary tract, cause urinary stagnation, increase the susceptibility of the urinary tract to infection and can lead to secondary kidney damage. The urine is dark and distinctly smelly, with an admixture of blood. Urination is painful and often unsuccessful. The first symptoms are usually seen between 7 weeks and 4 years of age.

In Dachshunds, the disease is caused by the c.137T>C mutation in the gene for molybdenum cofactor sulphurase (MOCOS). As a result of the mutation, the stop codon is introduced prematurely, and the resulting protein is truncated.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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References:

Tate, N.M., Minor, K.M., Lulich, J.P., Mickelson, J.R., Berent, A., Foster, J.D., Petersen, K.H., Furrow, E. : Multiple variants in XDH and MOCOS underlie xanthine urolithiasis in dogs. Mol Genet Metab Rep 29:100792, 2021. Pubmed reference: 34584846