Dominant Cystinuria Australian Cattle Dog Type (D-CYS)
Dominant cystinuria Australian Cattle dog type (D-CYS) is a congenital disorder of metabolism specific for Australian Cattle dog breed. It belongs in wider disorder group called Cystinuria that comprises defects in reabsorptive transport of cysteine and amino acids ornithine, arginine and lysine from renal proximal tubule and small intestine. It was for first time reported in 1823, as an inborn defect of metabolism in dogs. Today, cystinuria has been recognized to affect more than 70 dog breeds. Canine cystinuria can be divided into two groups, type I and non-type I cystinuria. Type I cystinuria is known to affect Newfoundlands and Landseers and is known as an autosomal recessive disorder which affects both male and female dogs. Non-type I cystinuria has been identified in Mastiffs and related breeds, Scottish Deerhounds and Irish Terriers. Mode of inheritance of non-type I cystinuria remains unknown, but it is established that it is not a X-chromosomal disorder and appears to be testosterone depended.
Characteristics and symptoms
Although cystinuria appears to be very heterogenic disorder among humans and dogs, different canine cystinurias are caused by a mutation in same genes. This mutations prevent reabsorption of positive charged amino acids cysteine, lysine, ornithine and arginine. In normal functioning kidney, these amino acids will be reabsorbed into the blood from the filtered fluid that will become urine. Cystinuria causing mutations result in malfunctioning transporter proteins for these amino acids, which causes their high levels in the urine and consequently crystals or stones formation. Formatted stones can cause blockage of the urinary tract, a severe condition that requires surgery and can cause death. These stones can also be a source of bacterial infection. All this can result in stranguria, hematuria, urinary obstruction and renal failure.
Cystinuria affected dogs can show following symptoms: frequent urination, blood in the urine, frequent urinary tract infections, difficult urination, scanty urination, evidence of pain during urination or any other abnormalities during dog’s urination.
Affected dog will not show any symptoms until already progressed stages of the disease. Due to risk and health complications that stones formation brings, it is important to detect cystinuria on time. Stones, when they reach appropriate size, can be detected with an x-ray or on an ultrasound.
Dominant cystinuria Australian Cattle dog type (D-CYS) is caused by an in-frame 6 bp deletion in the SLC3A1 gene. It is inherited as an autosomal dominant disorder and both homozygous and heterozygous for the mutation dogs will develop symptoms. Homozygous dogs appear to develop symptoms earlier than the heterozygous dogs and their symptoms appear to be more severe. Since cystinuria is not easily diagnosed and can cause dog to suffer from symptoms for long time before being identified, it is important to prevent breeding of dogs with mutated genes and obtaining affected cubs.
Brons, AK. (2013): SLC3A1 and SLC7A9 mutations in autosomal recessive or dominant canine cystinuria: a new classification system. J Vet Intern Med. 2013 Nov-Dec;27(6):1400-8. doi: 10.1111/jvim.12176. Epub 2013 Sep 3.