Tay-Sachs disease
Tay-Sachs disease is a genetic disorder caused by a deficiency of the enzyme hexosaminidase-A, which leads to the accumulation of certain lipids in the brain and spinal cord. This progressive condition primarily affects infants who typically appear normal at birth but begin to show symptoms such as deafness, blindness, and muscle paralysis between three and six months of age. Most children with Tay-Sachs do not survive beyond age four, as they succumb to complications from the disease.
Characteristic features, like cherry-red spots on the retina, may aid early detection. There is currently no cure for Tay-Sachs; treatment focuses on supportive care, including nutrition management and seizure control. The disease is particularly prevalent among individuals of Ashkenazi Jewish, French Canadian, and Cajun descent, with carrier rates significantly higher in these populations. Genetic counseling, carrier screening, and prenatal testing are important for at-risk couples. Despite the challenges, ongoing research into gene therapy offers hope for future treatment options.
Tay-Sachs disease
Anatomy or system affected: Nervous system
Definition: An inherited disorder in which products of fat metabolism (gangliosides) accumulate in and destroy the brain and spinal cord
Causes: Genetic disorder
Symptoms: Initially, cherry-red spots on retina; in later stages, deafness, blindness, muscle paralysis, developmental disorders, vegetative state
Duration: Three or four years, until death
Treatments: Supportive therapy only
Causes and Symptoms
Tay-Sachs disease is a genetic disorder of lipid (fat) metabolism resulting from a missing enzyme, hexosaminidase-A. This enzyme normally breaks down special nerve lipids known as gangliosides, which are present in the brain and spinal cord. These substances accumulate and destroy the cells, often killing the child by age three or four years.
Several features at birth may raise the possibility of early detection, particularly cherry-red spots on the retina of the eye. Most newborns with Tay-Sachs disease, however, appear normal at birth. Between the ages of three months and six months, the progressive neurologic damage becomes apparent: deafness, blindness, muscle paralysis, and developmental disorders. By eighteen months, the infant is usually already in a vegetative state, requiring complete care. The child may survive until three or four years of age, dying from complications associated with comatose and bedridden patients, usually infections.
A severe form of Tay-Sachs disease is called Sandhoff disease, and its effects become apparent around six months of age. Symptoms may include weakness, cherry-red spots and blindness, heart murmurs, respiratory ailments, seizures, involuntary muscle movements, declining central nervous system function, and enlargement of the head, liver, or spleen.
Treatment and Therapy
Tay-Sachs disease has no cure, and only supportive measures can be used. Feeding tubes for nutrition and fluids, suctioning of throat secretions, meticulous skin care for bed sores, and oxygen to assist breathing are among the types of support needed. Anticonvulsants may help with seizures. Full-time skilled nursing care at home or at a facility is often necessary.
Researchers have also explored the possibility of using gene therapy to treat or cure Tay-Sachs disease. In the late 2010s and early 2020s, two children were given the first successful round of gene therapy for the disease; by 2022, both children were still alive and had seen an improvement in their symptoms, namely relief from their seizures.
Perspectives and Prospects
While Tay-Sachs disease is the most common lipid (or lysosomal) storage disease, it is an autosomal recessive disorder rare in the general population—about 1 in 250 people carry the genetic mutation that causes Tay-Sachs. It is much more common, however, in Americans of Ashkenazi (Eastern European) Jewish ancestry, as well as those of French Canadian and Cajun ancestry. Among these populations, approximately 1 person in 27 is a carrier of the genetic defect. If two such carriers have children, they have a one-in-four chance of having a child with Tay-Sachs disease and a one-in-two chance of having a child who is a carrier.
Prenatal testing using chorionic villus sampling in the first trimester or amniocentesis in the second can detect affected fetuses. More important is genetic counseling and screening of couples with a family history. A blood test can identify carriers. Preimplantation diagnosis offers carriers the option of implanting only those embryos that do not carry the Tay-Sachs mutation through in vitro fertilization.
Ongoing research is attempting to correct the disease in the developing fetus through the insertion of the missing gene or by providing the missing enzyme to affected infants.
Bibliography
Bartoshesky, Louis E. "Tay-Sachs Disease." KidsHealth.org. Nemours Foundation, May 2011.
Behrman, Richard E., Robert M. Kliegman, and Hal B. Jenson, eds. Nelson Textbook of Pediatrics. 19th ed. Saunders/Elsevier, 2011.
Harper, Peter S. Practical Genetic Counselling. 7th ed. Oxford University Press, 2010.
Hollenstein, Jenna, and Kari-Kassir. "Tay-Sachs Disease." Health Library, Nov. 26, 2012.
Kolata, Gina. "Using Genetic Tests, Ashkenazi Jews Vanquish a Disease." The New York Times, 18 Feb. 2003, www.nytimes.com/2003/02/18/science/using-genetic-tests-ashkenazi-jews-vanquish-a-disease.html. Accessed 7 June 2022.
McCance, Kathryn L., and Sue M. Huether. Pathophysiology: The Biologic Basis for Disease in Adults and Children. 6th ed. Mosby/Elsevier, 2010.
Milunsky, Aubrey, ed. Genetic Disorders of the Fetus: Diagnosis, Prevention, and Treatment. 6th ed. Wiley-Blackwell, 2009.
Sena-Esteves, Miguel. "First Gene Therapy for Tay-Sachs Disease Successfully Given to Two Children." Scientific American, 15 Feb. 2022, www.scientificamerican.com/article/first-gene-therapy-for-tay-sachs-disease-successfully-given-to-two-children/. Accessed 7 June 2022.
"Tay-Sachs Disease." Mayo Clinic, 21 Jan. 2022, www.mayoclinic.org/diseases-conditions/tay-sachs-disease/symptoms-causes/syc-20378190. Accessed 9 Aug. 2023.
"Tay-Sachs Disease." National Institute of Neurological Disorders and Stroke, 7 Feb. 2023, www.ninds.nih.gov/health-information/disorders/tay-sachs-disease. Accessed 9 Aug. 2023.