NCL Description for Chihuahuas

Age of on-set of clinical signs: 13 - 21 months

Age of euthanasia: 2 years

Abnormalities often observed by the owner:
Mental changes: Aggression, decreased sense of smell
Changes in gait and posture: circling
Visual abnormalities: impaired vision
Seizures/convulsions: none observed in case reported
Other changes: none reported

Abnormalities observed upon clinical examinations:
Clinical neurologic changes: specific exam findings were not described
Clinical ophthalmic changes: loss of pupillary light reflexes
Visual abnormalities: visual dysfunction
Retinal changes: normal retinal exam
Electroretinography (ERG): not performed
Other clinical findings: none reported


Histopathology
Brain: Neuronal swelling throughout the CNS, with cytoplasmic accumulation of yellowish pigment granules (a storage product). This storage product demonstrates yellow-green autofluorescence, and stains in a pattern consistent with ceroid and lipofuscin. This storage product is thought to be a lipid-binding protein. Pigment deposition was most abundant in the neurons of the hippocampus and thalamus, and in the Purkinje cells of the cerebellum. Immunohistochemistry (GFAP) revealed astrocytosis; gemistocytes were present throughout the CNS, and laminar gliosis was present in the cerebral cortex. The cerebellum had loss of Purkinje cells, Bergmann glial proliferation, and a decreased molecular layer. Concurrent congenital hydrocephalus was also present in the case reported (dilated lateral and third ventricles, with open fontanelles); and no obstructive lesions were present.
Eyes: Retinal neurons were also swollen and contained pigment granules. These pigments stained positive with periodic acid Schiff, Schmorl method for lipofuscin, and oil red O for lipid.
Other organs and structures: no abnormalities were identified in other organs; no storage products were found in any tissues outside the CNS.

Mode of inheritance:Autosomal recessive inheritance is suspected.

Gene containing mutation: Unknown

References:

Kuwamura M, et al. Neuronal ceroid-lipfuscinosis and hydrocephalus in a Chihuahua. Journal of Small Animal Practice (2003); 44:227-230.