TDK conference 2010

A stone-forming material can usually be found in the composition of uroliths. Knowing this component the leading pathophysiological processes can be concluded. Dalmations’ excretion of uric acid instead of allantoin as an end product of purine metabolism is well known. Therefore the uric acid concentration in the urine is high which predisposes Dalmatians to the formation of purine uroliths.

A genetic defect is responsible for the change in the purine metabolism which was locked during their intensive selection for sharply demarcated black spotty fur. In the background the mutation of SLC2A9 gene causes the defect significantly reducing the function of an urate transporter. All Dalmatians are homozygous for this recessively inheriting gene.

Purine uroliths can also be found in other non-dalmatian breeds but there were no studies regarding the genetic background of this phenomenon. Some researchers assumed that non-dalmatian dogs forming purine uroliths could also be homozygous for the defective gene of hyperuricosuria. Hence the probability of purine uroliths’ occurrence in English Bulldog and Black Russian Terrier is higher than in other breeds, genes of some patients with purine uroliths were mapped and the mutated allele was found.

Our examinations were to determine the ratio in non-dalmation breeds of the Hungarian dog population in which the individual genetic endowment can be blamed for the purine urolithiasis. The study included non-Dalmatian individuals whose uroliths were examined in the Urolith Centrum of Budapest between June 2008 and July 2010 and later were proved to be purine uroliths. DNA was obtained and preserved from blood samples and was sent to the US for genetic testing. In 5 cases from 14 the mutation characteristic of Dalmatians and causing hyperuricosuria could be shown. Three English Bulldogs, one Russian Black Terrier and a mongrel were proved to be homozygous for the gene in question. Thus the mutated allele was not only found in the known breeds (English Bulldog and Russian Black Terrier) in Hungary but also in a mixed breed dog. This fact suggests that the mutated gene can be more widely spread - also in other breeds - than expected.