Retinal pigment epithelial dystrophy

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Characteristic changes on ophthalmoscopic examination of a dog with retinal pigment epithelial dystrophy[1]

Retinal pigment epithelial dystrophy is a genetic ophthalmic disease of dogs.

This disease is associated with neuroaxonal degeneration in English cocker spaniel and Briard breeds with systemic vitamin E deficiency in the absence of dietary insufficiency[2].

The disease is characterised by the accumulation of auto-fluorescent lipofuscin-like inclusions in the retinal pigment epithelium (RPE), which initially involves only non-pigmented RPE cells overlying the tapetum but subsequently spreads to all pigmented RPE cells. Secondary neuro-retinal degeneration occurs with a gradual loss of the outer nuclear layer and the subsequent atrophy and degeneration of the inner retina[3].

Clinically affected dogs present with neurological symptoms such as hemeralopia and in severe cases retinal detachment, ataxia, proprioceptive deficits, abnormal spinal reflexes and muscle weakness[4].

Low plasma concentrations of α-tocopherol are commonly observed, but are not pathognomonic for the disease[5].

Diagnosis is based on presenting clinical signs, histopathological evidence of lipofuschins in retinal samples and low blood α-tocopherol levels in Cocker spaniel or Briard breeds. A differential diagnosis would include progressive retinal atrophy.

Twice daily administration of 600 - 900 IU tocopherol is likely to restore plasma vitamin E concentrations to the normal range in most affected dogs[6].

References

  1. Merck Vet Manual
  2. McLellan GJ & Bedford PG (2012) Oral vitamin E absorption in English Cocker Spaniels with familial vitamin E deficiency and retinal pigment epithelial dystrophy. Vet Ophthalmol 15(2):48-56
  3. Lightfoot RM et al (1996) Retinal pigment epithelial dystrophy in Briard dogs. Res Vet Sci 60(1):17-23
  4. McLellan GJ et al (2003) Clinical and pathological observations in English cocker spaniels with primary metabolic vitamin E deficiency and retinal pigment epithelial dystrophy. Vet Rec 153(10):287-292
  5. McLellan GJ et al (2002) Vitamin E deficiency in dogs with retinal pigment epithelial dystrophy. Vet Rec 151(22):663-667
  6. Bedford PG (2009) Retinal pigment epithelial dystrophy in the Briard. Vet Rec 164(12):377