Retinal pigment epithelial dystrophy
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.
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.
Low plasma concentrations of α-tocopherol are commonly observed, but are not pathognomonic for the disease.
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.
- Merck Vet Manual
- 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
- Lightfoot RM et al (1996) Retinal pigment epithelial dystrophy in Briard dogs. Res Vet Sci 60(1):17-23
- 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
- McLellan GJ et al (2002) Vitamin E deficiency in dogs with retinal pigment epithelial dystrophy. Vet Rec 151(22):663-667
- Bedford PG (2009) Retinal pigment epithelial dystrophy in the Briard. Vet Rec 164(12):377