Tay-Sachs Disease is a rare inherited disorder that affects the central nervous system. Tay-Sachs disease is named after Warren Tay (1843 - 1927) and Bernard Sachs (1858 - 1944). Warren Tay was an opthalmologist who described a patient with a 'cherry-red spot' on the retina. Bernard Sachs was a neurologist who noticed various cases of the disorder. He also found out that most of the affected children he saw had European Jewish origins.
Tay-Sachs Disease is caused by a recessive gene - you must have two copies of the gene to have the disorder. The recessive gene responsible for Tay-Sachs disease causes an enzyme deficiency - affected children are missing a vital enzyme (called hexosaminidase A, or Hex-A).
Somebody with only one copy of the Tay-Sachs gene is called a carrier; only if two carriers have children will the disorder be present (there is a 1-in-4 chance of this). If a carrier and a non-carrier have children, none of their children will have Tay-Sachs disease (but some may be carriers). As with some other disorders, including Bloom's Syndrome, Tay-Sachs disease and its recessive gene are quite common in Ashkenazi Jews1. If you have a history of Tay-Sachs disease or Ashkenazi Jews in your family, it is recommended by most doctors that you have genetic counselling. If you are pregnant, amniocentesis can be used to find out if the baby will have Tay-Sachs or not (after the test, you can choose to abort a Tay-Sachs baby).
Children with Tay-Sachs disease seem normal at birth; most symptoms appear when the child is aged between three and six months. Development becomes retarded; the child does not seem alert and may lose muscle strength. The child may have difficulty turning over. Other symptoms that appear are deafness, blindness, severe constipation and seizures. In the final stages, the child will become paralysed and completely non-responsive. The 'cherry-red spots' can sometimes be seen on the retina. Laboratory blood tests can detect the enzyme deficiency present in the child - this can usually confirm a diagnosis. Children with Tay-Sachs disease rarely survive beyond the age of five.
There are other disorders caused by Hex-A absence or deficiency that often come under the name 'Tay-Sachs'. There is such a thing as late-onset Tay-Sachs disease, where adults have progressive deterioration of functioning in their nervous system. This is caused by decreased amounts of the Hex-A enzyme. Late-onset Tay-Sachs has only been recently recognised as a disorder, and much about it is still unknown. Prognosis and symptoms vary between individuals.
There is a third form where the symptoms develop between ages two and six, and death occurs before age 15.
Sadly, there is no cure or treatment for Tay-Sachs disease, however some symptoms can be controlled (anti-convulsants, for example, can help with the seizures). Children with Tay-Sachs disease will almost definitely not be able to attend school; they may be confined to bed as the disease progresses. They need almost constant care.
1 A Jewish group specifically linked to German culture, with settlements around the world. In America, about one in 30 people from Ashkenazi Jewish descent is a carrier.