When do you begin to test for tay-sach's?

In infancy. Tay sachs is a degenerative disorder that presents with an exaggerated startle response (~6 months) and has a "cherry red spot" in the retina. Specific testing is for hexaminidase enzyme deficiency either alone or as a lysosomal enzyme screen that will look for related diseases (sandoff, krabbe). Early diagnosis allows the parents to know recurrence (25%) and consider prenatal testing.