Autosomal recessive inherited gangliosidosis characterized by the onset in the first 6 months of life of an exaggerated startle response, delay in psychomotor development, hypotonia (followed by spasticity), visual loss, and a macular cherry red spot; hexosaminidase a is deficient, leading to the accumulation of gm2 ganglioside in neurons of the central nervous system and retina; this condition is strongly associated with ashkenazic jewish ancestry.