An inherited condition in which harmful chemicals accumulate in the brain
Tay–Sachs disease is a fatal childhood disorder that is most common in the Ashkenazi Jewish population. The condition is caused by the lack of a vital enzyme in the brain. Without the enzyme, abnormal chemicals build up, leading to progressive and fatal brain damage. Tay–Sachs disease is caused by an abnormal gene that is inherited in an autosomal recessive manner (see Gene disorders). About 1 in 25 Ashkenazi Jews is a carrier of the abnormal gene, compared with about 1 in 250 in the non-Jewish population.
A baby who has Tay–Sachs disease often appears healthy at birth. The symptoms, which usually start to appear at 3–6 months of age, may include:
Exaggerated startle response to noise.
Muscle weakness and floppy limbs.
Lack of awareness of surroundings.
An affected baby may have seizures and gradually become paralysed during the first 6 months of life.
If the doctor suspects that your baby has Tay–Sachs disease, he or she may arrange for a blood test or a test on a sample of skin tissue to confirm that the enzyme is missing. The doctor will also examine the baby’s eyes to look for the presence of an abnormal “cherry-red spot” on the retina (the layer of light-sensitive cells at the back of the eye). There is no cure for Tay–Sachs disease, but an affected child will be made as comfortable as possible by treating symptoms as they arise.
People who are at risk of having a child with Tay–Sachs disease can be screened for the abnormal gene before marriage or pregnancy. If both partners are carriers of the gene, there is a 1 in 4 chance of their child being affected. The couple will be offered genetic counselling to explain these risks and discuss the options. Affected couples may decide not to have children or to conceive using IVF treatment (see Assisted conception), so that the embryo can be tested for the disease before implantation in the uterus.
Tay–Sachs disease is a fatal disorder, and children with the disease do not usually survive beyond the age of 5.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.