Fanconi's syndrome

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Iatrogenic Fanconi's syndrome, commonly reported following idiosyncratic reactions to preservatives in some dog treats

Primary Fanconi's syndrome is a rare adult-onset autosomal-dominant genetic renal disease of Basenji dogs caused by proximal renal tubular dysfunction and characterized by glycosuria in the face of euglycaemia.

Approximately 10% of adult Basenjis have Fanconi’s syndrome[1] and because this may not be diagnosed until later in life, subclinically-affected dogs may pass on the disease to their offspring.

The defect in the proximal renal tubule is believed to be due to a failure of endocytosis by the proximal tubule of glucose and proteins filtered by the glomerulus but may vary between the inherited and acquired forms of the syndrome[2].

Fanconi's syndrome can occur as a secondary phenomenon as a result of various renal insults from ingested toxins, infections or idiosyncratic drug reactions that collectively damage the proximal renal tubule and interrupt normal functioning[3].

Idiopathic Fanconi's (where no cause has been established) has been reported as well in the Norwegian Elkhound, Labrador Retriever[4], Shetland Sheepdog and Miniature Schnauzer.

Secondary Fanconi’s syndrome has been associated with a number of primary disease states, including:

Clinical symptoms in these affected dogs include lethargy, vomiting, anorexia, diarrhea, polyuria, polydypsia, weight loss and generalized weakness. Seizures have also been reported in approximately 15% of cases[11].

A tentative diagnosis is suggested by hematological changes including azotemia, high liver enzyme activities and hyperchloremic metabolic acidosis.

Urinalysis characteristically shows aminoaciduria and the presence of glucosuria[12]. Renal clearance studies often show decreased creatinine clearance and increased renal fractional excretion of sodium, potassium, calcium, and phosphorus[13].

A definitive diagnosis is one of exclusion, requiring a negative serology for Leptospirosis, serum fructosamine ≤250 μmol/L[14] (to exclude subclinical diabetes) and a renal biopsy which confirms proximal renal tubular nephropathy[15]

A differential list of other causes would include cystitis and infections with Rickettsia spp and Leptospira spp[16].

Fanconi’s syndrome is a progressive disease, which, if not treated, ultimately results in renal failure, due to proximal renal tubular acidosis[17]. Compensatory polypnea may forestall metabolic acidosis but without intervention, is invariably fatal[18].

The traditional treatment for Fanconi’s syndrome was administration of potassium citrate[19], but oral alkali supplementation with sodium bicarbonate appears more efficacious at maintaining longevity[20].

Dietary alkali supplementation should be provided lifelong, as the affected dogs continuously lose bicarbonate into the urine. The increased amount of solutes in the urine causes an osmotic diuresis and an inability to concentrate urine. Therefore, it is important that affected dogs always have access to water[21].

The prognosis in most cases is good providing proper veterinary intervention is instigated before significant renal damage occurs.

References

  1. Bax HA (2005) Inventory of Fanconi syndrome in Basenji dogs in The Netherlands. Tijdschr Diergeneeskd 130(16):472-474
  2. Ganong W (2001) Review of Medical Physiology. McGraw Hill Co., NY, pp:675-695
  3. Latimer KS, et al (2003) Duncan & Prasse’s Veterinary Laboratory Medicine: Clinical Pathology, 4th ed. Iowa State Press, Ames, Iowa, pp:183
  4. Jamieson PM & Chandler ML (2001) Transient renal tubulopathy in a Labrador retriever. J Small Anim Pract 42(11):546-549
  5. Darrigrand-Haag RA et al (1996) Congenital Fanconi syndrome associated with renal dysplasia in 2 Border Terriers. J Vet Intern Med 10(6):412-419
  6. Abraham LA et al (2006) Transient renal tubulopathy in a racing Greyhound. Aust Vet J 84(11):398-401
  7. Brown SA (1989) Fanconi’s syndrome inherited and acquired. In: Kirk R. Current Veterinary Therapy. W.B. Saunders Co., pp:1163-1165
  8. Appleman EH et al (2008) Transient acquired fanconi syndrome associated with copper storage hepatopathy in 3 dogs. J Vet Intern Med 22(4):1038-1042
  9. Hill TL et al (2008) Concurrent hepatic copper toxicosis and Fanconi's syndrome in a dog. J Vet Intern Med 22(1):219-222
  10. Freeman LM et al (1994) Fanconi's syndrome in a dog with primary hypoparathyroidism. J Vet Intern Med 8(5):349-354
  11. Yearley JH et al (2004) Survival time, lifespan, and quality of life in dogs with idiopathic Fanconi syndrome. J Am Vet Med Assoc 225(3):377-383
  12. Bovee KC, et al (1978) Spontaneous Fanconi syndrome in the dog. Metabolism 27:45-52
  13. Settles EL & Schmidt D (1994) Fanconi syndrome in a Labrador retriever. J Vet Intern Med 8(6):390-393
  14. Thoresen SI & Bredal WP (1999) Serum fructosamine measurement: a new diagnostic approach to renal glucosuria in dogs. Res Vet Sci 67(3):267-271
  15. Hostutler RA et al (2004) Transient proximal renal tubular acidosis and Fanconi syndrome in a dog. J Am Vet Med Assoc 224(10):1611-1614
  16. Hooper AN & Roberts BK (2011) Fanconi syndrome in four non-basenji dogs exposed to chicken jerky treats. J Am Anim Hosp Assoc 47(6):e178-187
  17. Brown SA, et al (1986) Fanconi syndrome and acute renal failure associated with gentamicin therapy in a dog. J Am Animal Hosp Assoc 22:635-640
  18. Hsu B, et al (1992) Membrane fluidity and sodium transport by renal membranes from dogs with spontaneous idiopathic Fanconi’s syndrome. Metabolism 41:253-259
  19. Yearley JH, Hancock DD, Mealey KL (2004) Survival time, lifespan, and quality of life in dogs with idiopathic Fanconi syndrome. J Am Vet Med Assoc 225(3):377-83
  20. Noonan CH, Kay J (1990) Prevalence and geographic distribution of Fanconi syndrome in Basenjis in the United States. J Am Vet Med Assoc 197:345-349
  21. Bartges JW (2000) Disorders of renal tubules. In: Ettinger SE: Textbook of Veterinary Internal Medicine. Diseases of the Dog and Cat. W.B. Saunders Co., Philadelphia, pp:1708-1709