Primary Hyperoxaluria

Primary hyperoxaluria is a very rare metabolic disease that causes increased production of oxalate, a substance that can form crystals in the kidney and other organs.

Symptoms

Symptoms of primary hyperoxaluria in dogs are severe and manifest at 3-4 weeks of age. These may include excessive thirst and urine output, presence of blood in the urine, abdominal pain, loss of appetite, weight and lethargy.

Disease Management

Unfortunately there is no cure for primary hyperoxaluria and it is a serious condition. Affected dogs usually die or are euthanized within the first two months of life.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Primary hyperoxaluria is characterized by the accumulation of glyoxylate and the subsequent synthesis and excretion of oxalate and glycolate, resulting in the precipitation of calcium oxalate in tissues, mainly in the kidneys. Calcium oxalate accumulates progressively in the form of stones in the tubules of the renal cortex that can lead to renal failure. The AGXT gene encodes for the enzyme alanine glyoxylate aminotransferase, a liver enzyme found in cellular peroxisomes and involved in glyoxylate detoxification. Here we analyzed the c.304G>A variant, also known as p.Gly102Ser, of the AGXT gene that was identified in Finnish Coton de Tulear dogs. This variant causes disease when present in homozygosis and affects an amino acid that is strictly conserved in multiple species, suggesting that the affected amino acid has a relevant role for structure or function of the enzyme.

Most affected breeds

Coton de Tulear
Tibetan Spaniel

Bibliography

Vidgren G, Vainio-Siukola K, Honkasalo S,et al. Primary hyperoxaluria in Coton de Tulear. Anim Genet. 2012 Jun;43(3):356-61.