GM1 Gangliosidosis Portuguese Water Dog Type is a congenital lysosomal disorder affecting the Portuguese Water Dog breed.

It is a progressive neurodegenerative disorder with a fatal outcome.

GM1 belongs in a group of lysosomal disorders known as gangliosidosis, caused by the accumulation of lipids gangliosides.

In the gangliosidoses group of disorders, other than GM1, belongs another disorder type, known as GM2.

There are three forms of GM1: early infantile, late infantile, and adult.

Except in Portuguese Water Dogs, GM1 has been reported in Friesian cattle, Siamese and Korat cats, English springer spaniels, and mixed breed beagle dogs.

Beta-galactosidase is a hydrolase enzyme located in the lysosomes.

It catalyzes breakage of a glycosidic bond, resulting in the hydrolysis of beta-galactosides into monosaccharides.

When the gene encoding for beta-galactosidase enzyme is deficient, abnormal storage of acidic lipid materials in cells of the central and peripheral nervous system occurs.

GM1 is characterized by low or absent activity of this enzyme in brain and liver.