Cystinuria is an inherited metabolic disorder characterized by abnormal transport of certain amino acids in the intestinal epithelium and proximal renal tubule. Due to the accumulation of high concentrations of cystine in the urine and its poor solubility in water, it percipitates out and can form cystine stones. The urinary stones, that cause clinical symptoms, can occur at the age of 4-6 months. This can lead to life-threatening closure of the urinary tract.

Cystinuria is a well-known hereditary metabolic disorder that leads to the formation of urinary stones and urinary obstruction. It has now been described in over 70 breeds. New studies have shown that this disease is very heterogeneous in terms of inheritance, mutation, frequency, severity, treatment and symptoms. A distinction is now made between the following subtypes of cystinuria affecting the different breeds:

The designation of type I cystinuria is used when the disease shows autosomal recessive inheritance, Type II when inheritance is autosomal dominant, and Type III for sex-limited/androgen-dependent inheritance (PH, UG, unpublished data). Additional types can be assigned if found. Specific mutations within each type should lead to phenotypes that are sufficiently similar that the same medical management and breeding advice applies to all cases within that type. Involvement of the SLC3A1 gene is indicated by adding - A, and similarly addendum of - B indicated involvement of mutations in SLC7A9.

• Newfoundland, Landseer, Labrador: Type I -A - autosomal recessive inheritance
• Miniature Pinscher: Type I - B - autosomal dominant inheritance
• Australian Cattle Dog: Type II - A - dominant inheritance
• Mastiff, Bulldogs, Kromfohrländer and Irish Terrier: Type III - androgen-dependent expression.

The type III genetic test has been available for the breeds Mastiff, Continental, English, French and Olde English Bulldogs since December 2016. We test for a marker which is strongly associated with the occurrence of cystinuria. Type III Cystinuria affects only intact male dogs which have two copies of the cystinuria marker (cy/cy). Castration can alleviate the symptoms. Bitches do not show any symptoms but pass on the mutation to offspring.

Prevalence: between 8 and 16% of the dogs are genetically affected, while the carrier rate is between 32 and 50%. Targeted breeding reduces the frequency of the marker associated with the disease and is therefore desirable. Due to the high frequency of the gene, it is advisable that carriers should not taken out of breeding in order maintain the diversity of the gene pool. Dogs (Males or Females) tested Carriers (N/cy) should only be bred with clear dogs (N/N). Bitches tested genetically affected (homozygous for the mutation) (Cy/Cy) should not be removed from breeding but should only be bred with clear dogs (N/N). Mating with free animals is possible without any problems. The Labogen team will be happy to answer any further questions you may have.