Test Overview

This test for Tay-Sachs disease measures the amount of an enzyme called hexosaminidase A (Hex A) in the blood. Hex A breaks down fatty substances in the brain and nerves. Tay-Sachs is an inherited disease in which the body can't break down fatty substances as it should, so the fatty substances collect in the nerve cells of the brain and damage them.

Tay-Sachs can occur when parents pass on a changed gene to their child.

• If the changed gene is from both parents, the baby will get the disease.
• If the changed gene is from only one parent, the baby will be a carrier. This means that the child will have one gene that produces Hex A and one that doesn't. The child's body makes enough Hex A so they won't get the disease. But the child can pass the changed gene on to their children.

The Tay-Sachs enzyme test is usually done on blood taken from a vein or from the umbilical cord right after birth.