GM2 Gangliosidosis Poodle Type is a congenital lysosomal disorder affecting the Poodle and it is known as GM2 Gangliosidosis variant 0. It is a progressive neurodegenerative disorder with a fatal outcome. GM2 belongs in a group of lysosomal disorders known as Gangliosidosis, caused by the accumulation of lipids known as gangliosides. In the Gangliosidosis group of disorders, other than GM2, belongs another disorder type, known as GM1. There are three variants of GM2 Gangliosidosis, 0, B and AB. Gangliosidosis variant 0 (GM2) has a human equivalent, known as Sandhoff disease, while in animals, GM2 has been identified in dogs, cats, pigs, deer and flamingos.
GM2 Gangliosidosis is a result of beta-hexosaminidase (Hex) deficiency, an enzyme that catalyzes the biodegradation of lipids gangliosides. This hydrolytic enzyme can be found in lysosomes. Hex is composed of two main isoenzymes, Hex A and Hex B, while only Hex A acts as the GM2 activator protein. Defects in the genes encoding for named proteins causes their improper function. In case of unfunctioning beta-hexosaminidase enzyme, gangliosides start to accumulate, especially in the lysosomes of neurons, causing problems.
Symptoms
Symptoms start to occur in the affected dog around 9 to 12 months of age. Neurological symptoms include stiff gait, loss of balance, falling ataxia, intention tremor, postural deficit, astasia, decreased menace response, vision defect or loss, decreased corneal reflex, and decreased level of consciousness. In most of affected dogs another symptom was vomiting, without known reason. Common finding in affected Toy Poodles was diffuse T2-hyperintensity of the subcortical white matter in the cerebrum, caused by hypoplasia of the myelin or delayed myelination, or both.
In general, clinical signs of GM2 Poodle Type are similar to those recognized previously in a Golden Retriever with GM2, with same age of symptom onset. Main noticed difference between GM2 Poodle type and Golden Retriever type was loss of pupillary light reflexes, which was not recorded in Poodles.