This is one of the gangliosidosis and is the most common one. It is caused by a deficient subunit A of hexosaminidase. The mechanism is a ganglioside buildup in the brain and retina which causes mental retardation and blindness. Most of these children die between ages 2 and 5. In the retina you can see a cherry red spot as this is the only area that is not filled with ganglioside (thus, a normal fovea).
