What is Autosomal Hereditary Recessive Nephropathy in dogs?

Autosomal Hereditary Recessive Nephropathy (AHRN) is an inherited kidney disease that leads to renal (kidney) failure that has been recognised in dogs worldwide. Autosomal Hereditary Recessive Nephropathy (also known as Familial Nephropathy) starts when the dog is still a young dog of between 6 months and 2 years old and progresses in a similar pattern for every dog affected. At it’s simplest explanation, the disease affects the collagen that makes up the internal structure of the kidneys preventing them from performing their function as the body’s filtration system.

Genetics of Autosomal Hereditary Recessive Nephropathy

The name of this disease lets us know that there is a genetic cause arising from the autosomal genes of the dog that has a recessive mode of inheritance known as Autosomal Recessive. This means that a copy of the mutated gene must be inherited from both the mother and father of the puppy for it to be affected.  In this case the gene responsible is the COL4A4 gene and its mutation leads to dogs having Autosomal Hereditary Recessive Nephropathy. Point Mutations of this gene have been reliably shown to determine if a dog will be affected by this condition.

What is the severity of Autosomal Hereditary Recessive Nephropathy?

Autosomal Hereditary Recessive Nephropathy is classified in the highest severity range as the disease affects young dogs with a high degree of morbidity with a fatal outcome.  While all dogs go through the same process of symptoms, there is some slight differences between individuals as to the rate of decline owing to a different rate of kidney dysfunction between individual dogs.

What are the symptoms of Autosomal Hereditary Recessive Nephropathy in dogs?

Initial symptoms of Autosomal Hereditary Recessive Nephropathy include excessive water consumption (polydipsia), excessive urine volume (polyuria), reduced growth rate or weight loss, reduced appetite, poor quality hair and coat and vomiting. As the disease progresses and kidney function deteriorates other symptoms of a very ill dog including thin body condition, dehydration, pale colour of mucous membranes, uremic breath odour, and oral ulcerations will become evident.

Diagnosis of Autosomal Hereditary Recessive Nephropathy

Early diagnosis of Autosomal Hereditary Recessive Nephropathy can easily be missed as frequent urination and excessive water consumption is often mistaken for the normal behaviour of active puppies. It is often the more severe symptoms that will be the first signs that something is wrong with the dog. A DNA test for the mutated COL4A4 gene is the most definitive way of diagnosing Autosomal Hereditary Recessive Nephropathy in dogs.

Treatment of dogs with Autosomal Hereditary Recessive Nephropathy

Unfortunately there is no cure for Autosomal Hereditary Recessive Nephropathy and only supportive care can be offered to affected dogs as their renal failure worsens. A decision to euthanase the dog is often made before the dog suffers any further.

Preventing Autosomal Hereditary Recessive Nephropathy in dogs

DNA testing of parent dogs prior to breeding is the only way to prevent dogs from developing this fatal disease. The DNA test pioneered by Dr.  George Lees and his research team for a point mutation of the COL4A4 gene will identify clear, carrier and affected dogs for this condition.

References

Ashley G. Davidson, Rebecca J. Bell, George E. Lees, Clifford E. Kashtan, George S. Davidson, Keith E. Murphy “Genetic Cause of Autosomal Recessive Hereditary Nephropathy in the English Cocker Spaniel” Journal of Veterinary Internal Medicine Volume 21, Issue 3,pages 394–401, May 2007
Davidson AG, Bell RJ, Lees GE, Kashtan CE, Davidson GS, Murphy KE. Genetic cause of autosomal recessive hereditary nephropathy in the English Cocker Spaniel. J Vet Intern Med. 2007 May-Jun; 21(3):394-401.
Lees GE, Wilson PD, Helman RG, Homco LD, Frey MS. (1997) Glomerular ultrastructural findings similar to hereditary nephritis in 4 English cocker spaniels. Journal of Veterinary Internal Medicine. 11(2):80-5.
Lees GE, Helman RG, Kashtan CE, Michael AF, Homco LD, Millichamp NJ, Ninomiya Y, Sado Y, Naito I, Kim Y. (1998) A model of autosomal recessive Alport syndrome in English cocker spaniel dogs. Kidney Int. 54(3):706-19.
Robinson WF; Huxtable CR; Gooding, JP. (1985) Familial nephropathy in cocker spaniels. Australian Veterinary Journal. 62: 109-112.