TAY-SACHS DISEASE

TAY-SACHS DISEASE (Amaurotic Familial Idiocy). Amaurotic Familial Idiocy, known as the Tay-Sachs Disease after W. Tay, an English ophthalmologist who discovered it in 1881, and B. Sachs, a U.S. neurologist who followed in 1887, is a hereditary disease, characterized by the onset during the first year of life of progressive retardation of development, followed by dementia, blindness, and paralysis. The outcome is invariably fatal by the third or fourth year of life. The disease has a predilection for children of Ashkenazi Jewish families, with about 90 percent of all cases occurring in Jewish children whose antecedents are from families originating in the Polish-Russian provinces of Grodno, Suwalki, Vilna, and Kaunas (Kovno). The disease is carried by autosomal recessive genes and occurs only when both parents are carriers. The combination of both affected genes in the child occurs, according to Mendelian Theory, in 25% of cases, with all these children developing the disease. The eponym Tay-Sachs, while originally all-inclusive, is today restricted to the infantile type of amaurotic idiocy, while five other variants of this disease which have been described are associated with other eponyms. The clinical signs and symptoms primarily affect the central nervous system. Recent research has demonstrated that the disease is caused by a genetically determined metabolic defect, leading to the accumulation within cells of the brain of abnormal quantities of gangliosides, complex fatty substances of the sphingolipid family. The genetic defect is caused by the deficient activity of a specific enzyme (Hexosaminidase A) required in biochemical reactions for the breakdown of a ganglioside, GM₂. This deficiency leads to accumulation of these fatty substances in the blood and their deposit in the tissues, subsequently associated with degenerative changes. The Kingsbrook Jewish Medical Center (formerly the Jewish Chronic Disease Hospital) in New York City has been a center for research and treatment of the disease and has the largest experience in caring for its victims. There is no specific treatment of the disease, but supportive care in units especially skilled in handling such children provide considerable help to parents and temporarily improve the immediate prognosis of the affected child. The development of methods for the assay of blood serum Hexosaminidase A activity has led to the introduction of tests which make it possible to discover carriers of the gene causing the disease. Jewish community organizations and health centers in various parts of the United States and in Israel have sponsored screening programs for the detection of the carrier state in couples considering marriage. When both are carriers, they may be counseled to avoid marriage or not to have children. Similar biochemical studies are possible on the amniotic fluid of pregnant women to determine if the fetus is affected by the disease. This test permits near-accurate prenatal diagnosis of the disease. In such cases abortion is often advised. Since Tay-Sachs disease is primarily a disease of Jews and the performance of abortion has religious and moral aspects, the permissibility of abortion where the disease has been diagnosed   in the fetus has been discussed by rabbinic authorities. Rabbinical responsa in general oppose abortion in Tay-Sachs. As the detection of the disease in the fetus is still very difficult before the completion of three months of pregnancy, those rabbinical authorities who limit interruption of pregnancy in cases of fetal malformation (German measles) to the first three months of pregnancy, do not consent to an abortion in Tay-Sachs disease. Rabbi E.J. Waldenberg, however, permits abortion because of Tay-Sachs up to seven months of pregnancy, in view of the tragic nature and inevitable effect upon a child born with this disease. -BIBLIOGRAPHY: Stanbury, Wyngaarden and Fredrickson, The Metabolic Basis of Inherited Disease (1972); R.H. Post, in: Lancet (June 6, 1970) 1230–1. (David M. Maeir)