The Collaborative International Dictionary of English v.0.48:

Tay-Sachs Disease \Tay"-Sachs Disease\, n. (Med.)
   A rare hereditary disease affecting lipid metabolism in
   humans, due to a deficiency of hexosaminidase. It occurs in
   infants and children, and causes death before the onset of
   adulthood. It occurs most commonly of people of Jewish origin
   from easter Europe. It is characterized by accumulation of
   lipids in nervous tissue, causes a red spot on the retina,
   and eventual blindness and paralysis before death.
   [PJC]

WordNet (r) 3.0 (2006):

Tay-Sachs disease
    n 1: a hereditary disorder of lipid metabolism occurring most
         frequently in individuals of Jewish descent in eastern
         Europe; accumulation of lipids in nervous tissue results in
         death in early childhood [syn: Tay-Sachs disease, Tay-
         Sachs, Sachs disease, infantile amaurotic idiocy]