A rare metabolic disorder characterized by an accumulation of lipid (fat) in the nerve cells of the brain, resulting in severe mental retardation. The disease was first described by the English physician, Warren Tay (1843- 1927) and the American neurologist Bernard Sachs (1858-1944).Tay-Sachs is hereditary and transmitted by a single gene. It is found primarily but not exclusively in Jewish families originating in certain areas of eastern Europe. The infant appears normal at birth, but within a year grows increasingly apathetic and weak, and cannot hold his head steady or grasp objects firmly. Later symptoms include progressive spastic paralysis, seizures, and blindness (amaurosis). Victims of the disease usually fail to survive beyond the third year. Juvenile and adolescent forms of amaurotic idiocy also occur, and in these cases the patient may survive for about ten years after onset