Abstract
Purpose: :
To characterize hereditary neuronal ceroid lipofuscinosis (NCL) in the Polish Owczarek Nizinny (PON) dog using clinical and morphological methods.
Methods: :
Nine closely related dogs, 1.5–8 years old, were used for evaluation of systemic abnormalities and specific ophthalmic and neurologic changes. Ophthalmic studies included examination of pupillary light reflexes (PLRs), ophthalmoscopy and full–field electroretinography (ERG), the latter using commercial ERG equipment and a protocol for evaluation of rod and cone function. Tissues from all dogs were obtained for histopathological studies including immunocytochemistry, light– and electron microscopy (EM), with methods previously described.
Results: :
Behavioral abnormalities, motor disturbances, visual impairment, abnormal PLRs and funduscopic changes were found in the affected dogs. ERGs showed variable changes from nearly normal to non–recordable responses. Definite diagnosis of NCL was obtained through histopathologic findings of intracytoplasmatic storage bodies within neurons of the cerebral cortex, brain stem and retina. In 6 of the cases degenerative changes were observed in photoreceptors and the retinal pigment epithelium (RPE) was hypertrophied with large amounts of PAS positive inclusion bodies. EM clearly delineated granular osmophilic dense deposits (GRODS) in brain and/or retina in all cases, further identified by immunocytochemistry to be sphingolipid activator proteins (SAPs).
Conclusions: :
The NCL disease of PON dogs show few similarities to previously recorded cases in dog breeds with the exception of cases reported in the Miniature Schnauzer. The closest human equivalent is the infantile NCL (CLN1), in which the major stored proteins are SAPs and the ultrastructure of the inclusion bodies found is granular. Molecular genetic studies are in progress.
Keywords: degenerations/dystrophies • immunohistochemistry • visual impairment: neuro-ophthalmological disease