Tay-Sachs disease is arare and usually fatal genetic disorder that causes progressive damage to the nervous system.

Symptoms usually beginbefore ababy issix months old. Their development slows downand they gradually lose their ability to move.

The most noticeable early symptoms include a baby being excessively startled by sudden noises and red dots appearing near the middle oftheir eyes.

The childthen develops problems such as muscle weakness,loss of vision, loss of hearing and seizures.

Most children with the condition die before they're four years old.

Less common forms of Tay-Sachs disease can begin later in childhood or even early adulthood. These usually progress less rapidly, although it'susually fatal.

A genetic mutationis apermanent alteration in the DNA sequence that makes up a gene. It causes one or more processes of the body tonot work properly.

A mutated HEXAgene results in the body not producing an enzyme called Hexosaminidase-A (Hex-A). Without this enzyme, a fatty substance called GM2 ganglioside builds up in the cells of the brain and nerves, and stops themworking normally, eventually destroying them.

Both parents have to be carriers ofa HEXA mutation to be at risk of having a child with Tay-Sachs disease. If both parents are carriers, their children will have a 25% chance of developing the condition.

If the condition is diagnosed in an unborn baby,the parents can decide whether or not to continue with the pregnancy.

Most Jewish people in the UK are Ashkenazi Jews.

It's thought that around 1 in 25 Ashkenazi Jewish people are carriers of the mutated gene that causes Tay-Sachs disease.

However, with screening, the condition is now rare and most cases now occur in people who aren't of Ashkenazi Jewish descent. It's estimated that only about 1 in every 360,000 children born worldwide has Tay-Sachs disease.

Information about your child

If your child has Tay-Sachs disease, your clinical team will pass information about him or her on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).

This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.

Find out more about the register.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 5 Dec 2016