GM1 gangliosidosis disease is caused by the absence or significantly reduced level of a vital enzyme called beta-galactosidase (GLB1). Without GLB1, a fatty substance or lipid called GM-1 ganglioside accumulates abnormally in cells, especially in the nerve cells of the brain. This ongoing accumulation, also called "substrate", causes progressive damage to the cells.
The Juvenile and adult Late Onset forms of GM1 gangliosidosis occur when the mutations allow the GLB1 enzyme to function a little bit. Just a small increase in GLB1 activity is enough to delay the onset and slow the progression of symptoms.
The gene that causes GM1 gangliosidosis is located on chromosome 3, specifically 3p21.33.
GM1 gangliosidosis is an autosomal recessive genetic disorder. Both parents must be a carrier for children to be at risk. There is a 25% chance with each pregnancy the child will be affected.
GM1 gangliosidosis "breeds true" in a family. If one child is diagnosed with infantile GM1 gangliosidosis the other children are only at risk for the infantile form. One set of parents could not have children with both the infantile and juvenile forms of the disease.
Read more About Autosomal Recessive Inheritance