Tay-Sachs disease is a fatal genetic lipid storage disorder in which harmful quantities of a fatty substance called ganglioside GM2 build up in tissues and nerve cells in the brain.  There are three (3) types of Tay-Sachs disease, categorized by the symptoms and the age when the symptoms first appear.  The most common type appears when the child is 3 to 6 months old - the disease progressing rapidly to death by age 4 or 5.  At birth, the infant appears healthy and develops normally for the first few months of life, but as the buildup of ganglioside GM2 begins to affect nerves, symptoms appear.  A rare from of Tay-Sachs – develops later in life – is due to low levels of the hex A enzyme, rather than the complete deficiency of hex A in the infantile form. Children with juvenile hex A deficiency develop symptoms between ages 2 and 5, and usually die by age 15. A milder form of hex A deficiency can develop anywhere from age 5 to the early 30s.