Gangliosidosis

Ganglioside storage diseases, or gangliosidoses, are inherited (autosomal recessive) defects of lysosomal hydrolase enzymes that result in accumulation of gangliosides (substances that are major constituents of plasma membranes in a variety of cells, especially neurons, or nerve cells) throughout the nervous system, including brain, spinal cord, and autonomic ganglia. In dogs and cats, several gangliosidoses have been identified and categorized according to the enzyme deficit and degree of internal organ involvement. GM1 gangliosidosis has been reported in cats (Siamese, Korat, and Domestic Shorthair), and dogs (English Springer Spaniel, Portuguese Water dog, mixed-breed Beagle, huskies, Shiba, and cross-breed dogs).

GM1 variant of gangliosidosis resulting from the accumulation of ganglioside in the brain is due to deficiency of acid Β-galactosidase. This deficiency results in accumulation of GM1 gangliosides in the lysosomes leading to lysosomal swelling, cellular damage, and organ dysfunction. The disease is lethal in the infantile and juvenile forms. Patients with infantile GM1-gangliosidosis are presented at birth or shortly thereafter with tissue and bony changes followed by severe neurological deterioration leading to death within the first years of life.

Clinical signs of GM1 gangliosidosis are first noted in dogs around 4 to 5 months of age and in cats from 2 to 5 months of age. Initial signs include weight loss, moderate wide-based gait, and a fine tremor of the head. At 7 months of age, diseased animals display dwarfism and show clinical neurological signs including poor movement coordination (ataxia). Frequent falling and swaying is noticed, and the head tremor becomes more obvious. Affected dogs continue to eat and drink, although at a decreased level. Some cats with GM1 gangliosidosis manifest enlarged liver (hepatomegaly) which may appear swollen.

Dog Breeds Affected by Gangliosidosis

The GM2 gangliosidoses are a group of heritable neurodegenerative disorders caused by excessive accumulation of the ganglioside GM2 owing to deficiency in beta-hexosaminidase enzyme activity. GM2 gangliosidosis has been reported in German Shorthair Pointers, Japanese Pointers, mixed-breed cats, and Korat cats. Four major enzymatic variants of GM2 gangliosidosis are recognized in people. In animals with GM2 gangliosidosis, onset of clinical signs is from 1 to 3 months of age in kittens, 6 to 12 months of age in German Shorthair Pointers ((these dogs also have coarse facial features), and around 18 months of age in Japanese Spaniels.

Signs of Gangliosidosis

Neurological signs are very similar in both species and are highlighted by their relentlessly progressive nature. Cerebellar-like signs of ataxia-dysmetria, head tremor, loss of balance, and abnormal nystagmus (early loss of central vision) are often the first signs observed, followed by spastic paraplegia or tetraplegia (severe or complete loss of motor function in the lower extremities and lower portions of the trunk), visual impairment, depression, sometimes dementia (mental disorder with loss of intellectual abilities), seizures, aggression, and death. Corneal clouding has been seen in feline GM1 and GM2 gangliosidosis.

A suspected lysosomal storage disease has been reported in Abyssinian kittens in which the clinical signs are very similar to those mentioned above.

The three approaches to providing normal enzyme to a patient's cells are enzyme replacement therapy (ERT), bone marrow transplantation (BMT) and gene therapy. In general, the most difficult target tissue in the LSDs is the central nervous system (CNS). Bone marrow transplantation early in life has been found to be ineffective in canine GM1 gangliosidosis.

Adapted from:
1. GM1 gangliosidosis: Review of clinical, molecular, and therapeutic aspects Nicola Brunetti-Pierria and Fernando Scaglia
2. Storage Disorders. K. G. Braund
3. GM1-gangliosidosis in Alaskan Huskies: Clinical and Pathologic Findings. G. MU LLER, S. ALLDINGER, A. MORITZ, A. ZURBRIGGEN, N. KIRCHHOF, A. SEWELL, AND W. BAUMGA RTNER