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There have been many questions recently regarding the comparison of Optigen and CERF's information with regards to PRA in Labs. It is important that one does not try to simply do a direct comparison of these two sets of numbers. Due to many factors these two sets of statistics will not match. For more information about this please see the article on OptiGen's web site at www.optigen.com.
Neuronal Ceroid Lipofuscinosis (NCL) is a hereditary, progressive, disease in dogs and humans, which commonly leads to blindness and other neurologic problems and can lead to premature death. It is a lipid storage disease, meaning that affected individuals have an abnormal ability to store fat-associate pigments (lipopigments) in their bodies. Many biochemical defects have been implicated in these lipid storage diseases. NCL causes degeneration of the retina and usually affects the central nervous system (the brain) as well.
NCL has been described in several breeds including the English setter, dalmatian, Border collie, Tibetan terrier, Polish Owczarek Nizinni (PON), and the miniature schnauzer.1 The hereditary mechanism by which this disease is transferred has been determined in only the English setter breed. In that breed it is inherited as an autosomal recessive trait.2
In most of the affected breeds the blindness caused by NCL is due to a brain dysfunction (abnormal storage of lipoproteins in the brain's visual cortex) rather than a problem in the eye itself. The exceptions to this are in Tibetan terriers, PONs and miniature schnauzers. In Tibetan terriers, night blindness due to accumulations of lipid-like material in the cells of the retina, occurs in young animals (as young as 2 months) and more severe neurologic problems, due to brain dysfunction, are not seen until later in life.3 In the PON, visual deficits and changes in the retinal examination findings may occur as early as 1 to 2 years of age and neurologic symptoms such as ataxia (loss of balance), muscle weakness and dementia may develop shortly after the onset of blindness. 4 In miniature schnauzers blindness develops at about 3 to 4 years of age and is often accompanied by neurologic signs,5 while in English setters, retinal function is normal at the time that other neurologic signs develop (at about l year of age) and blindness develops later. 2
NCL, in some breeds, may initially mimic progressive retinal atrophy (PRA). Tibetan terriers begin to have night vision problems early in life but changes in the retina, that look identical to the changes similar to those noted in dogs with PRA, often do not become evident until 3 to 4 years of age. 1 It is thus easy to mistake this disease for PRA until other neurologic symptoms manifest themselves.
It may be difficult to diagnose early cases of NCL but the electroretinogram (ERG) can provide clues. Characteristic abnormalities of the electrical waves produced by the retina and recorded as the ERG may help the ophthalmologist diagnose NCL. This test is particularly helpful in the Tibetan terrier in which abnormal ERG waves have been recorded as early as 7 weeks of age. These wave abnormalities are different from those produced by a retina that is affected with PRA. 3
NCL is a very serious, life-threatening disease in dogs. Breeders of dog breeds in which NCL has been reported should be aware of its manifestations and should have any dog exhibiting blindness or other neurologic diseases examined by an ophthalmologist. All dogs with this disorder, or a history of this disease in their lineage should be eliminated from the breeding population.
References
1. Narfstrom K, Ekesten B. Diseases of the Canine Fundus. In: Gelatt KN ed. Veterinary Ophthalmology 3rd edition Philadelphia, Lippincott, Williams and Wilkins, 1999;869-933.
2. Koppang N. Ceroid-lipofuscinosis in the English Setter; a review. In: Armstrong D, Koppang N, Rider JA eds. Ceroid-lipofuscinosis (Baten's disease). Amsterdam: Elsiver Biomedical Press, 1982;201-216.
3. Riis RC, Cummings JF, Loew ER, deLahunta A. Tibetan Terrier model of canine ceroid lipofuscinosis. Am J Med Genet 1992;42:615-621.
4. Wrigstad A, Nilsson SEG, Dubielzig R, Narfstrom K. Neuronal ceroid lipofuscinosis in the Polish Owczarek Nizinni (PON) dog. A retinal study. Doc Ophthalmol 1995;91:33-47.
5. Smith RIE, Sutton RH, Jolly RD, Smith KR. A retinal degeneration associated with ceroid-lipofuscinosis in adult Minitature Schnauzers. Vet Comp Ophthalmol 1996;6:187-191.
There have been some changes to our new addition of the Ocular Disorders book which came out in August 1999. Our genetics committee met in November and noticed a few things which need to be corrected in this book, which are as follows:
1. Mastiffs - Persistant Pupillary Membranes are rejected (All forms)
2. Alaskan Malamutes - Glaucoma is listed as ANY, this should be NO
3. Great Pyrenees - information on this breed was not included in the book but it is now available.
Please take note of these changes if you own the book. If you would like to obtain a copy of the guidelines for the Great Pyrenees, please contact our office.
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