Fanconi Syndrome

Other Names: Fanconi's syndrome, Paradoxic glucosuria
Affected Genes: FAN1
Inheritance: Autosomal Recessive
Mutation: Deletion
Breed(s): Basenji

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Common Symptoms

Fanconi syndrome is an inherited disorder of the kidneys affecting dogs. Affected dogs typically present with clinical signs of abnormal kidney function in adulthood with an average age of onset between four and eight years of age. Normally the kidneys reabsorb most of the nutrients and electrolytes that they filter from the blood. The kidneys of affected dogs do not properly reabsorb nutrients and electrolytes, such as glucose, protein, phosphate, potassium and sodium, and abnormally lose these nutrients in the urine. Symptoms of abnormal kidney function in affected dogs most commonly include increased urination and excessive drinking. Less often dogs may have weight loss despite a normal appetite, weakness, urinary incontinence and poor hair coat. A common characteristic of this disease is glucose in the urine with normal blood glucose levels. Fanconi syndrome is treatable but not curable. If an affected dog is not treated, the disease can progress to chronic kidney failure and overall poor health. Appropriate treatment can preserve the health and quality of life of affected dogs. The median survival time after diagnosis is five years with most dogs dying around 12 years of age. This late age of onset allows for most dogs to be bred before diagnosis and subsequently, the disease is passed to offspring.


Testing Tips

Genetic testing of the FAN1 gene will reliably determine whether a dog is a genetic Carrier of Fanconi syndrome. Fanconi syndrome is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the FAN1 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms typically do not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.


There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.


References

  • Farias FHG. Molecular genetic studies of canine inherited diseases [dissertation]. 2011. Retrieved from MOspace.
  • Johnson GS, Farias FH, Mhlanga-Mutangadura T, Taylor JF, O'Brien DP, Schnabel RD. Whole genome sequencing reveals a deletion of the last exon of FAN1 in Basenji dogs with adult-onset Fanconi syndrome [abstract]. Presented at the 63rd Annual Meeting of the American Society of Human Genetics in San Francisco, California; 2012 Nov 6-10.
  • Noonan CH, Kay JM. Prevalence and geographic distribution of Fanconi syndrome in Basenjis in the United States. J Am Vet Med Assoc. 1990 Aug 1;197(3):345-9. [PubMed: 2391269]
  • Yearley JH, Hancock DD, Mealey KL. Survival time, lifespan, and quality of life in dogs with idiopathic Fanconi syndrome. J Am Vet Med Assoc. 2004 Aug 1;225(3):377-83. [PubMed: 15328712]