Tay-Sachs disease is a rare, fatal disorder most commonly diagnosed in babies around 6 months of age. There’s no cure for the disease, but scientists have a good idea of what causes it, how it worsens, and how to use genetic . Tay-Sachs is a disease of the central nervous system. It is a neurodegenerative disorder that most commonly affects infants. In infants, it is a progressive disease that is unfortunately always fatal. Tay-Sachs can also occur in teens and adults, causing less severe symptoms, although this occurs. Tay-Sachs disease -- adult onset: A rare inherited biochemical disorder involving the deficiency of an enzyme called Hexosaminidase A. There are two forms of the.