GM2 gangliosidosis is a rare genetic disorder that progressively destroys nerve cells in the brain and spinal cord. The most common form of the disease typically presents in infancy, but various other forms can present in childhood, adolescence, or even adulthood. GM2 gangliosidosis is sometimes called Tay-Sachs disease or HexA deficiency. The disorder is one of about 50 diseases that are classified as lysosomal storage disorders (LSD), where a genetic variation disrupts the normal activity of lysosomes in human cells