Tay-Sachs病是神经节苷脂贮积病GM2中的一种类型,患者由于 基因编码氨基己糖苷酶A( hexosaminidase a,hexA)α亚单位的基 因突变,酶活性缺失而不能使神经节苷脂降解而堆积所致 Tay-Sachs disease Clinical features Severe mental and physical deterioration beginning in infancy, death occurs at age 2 to 3 years Incidence about 1 in 3600 in Ashkenazi Jewish births about I in 360000 in most other population Genetics Autosomal recessive Gene location 15q23-Q24 Basic defect Mutations at the locus for the a subunit of hexosaminidase a Pathophysiology Deficiency or absence of the lysosomal enzyme hexosam inidase a leads to accumulation of ganglioside Gm2 mainly in neurons Prenantal diagnosis Possible by assay of fetal tissues(including cultured or uncultured amniotic fluid cells or cells of chorionic villi) for activ ity of the enzyme; also possible by dna techniques in suitable family Treatment None available Significance Example of a lethal autosomal recessive disorder with high frequency in a specific, genetically isolated population. One of the first disorders for which heterozy gote screening was carried out on a large scale, and one of the first metabolic disorders for which prenatal diagnosis was used 其他一些常见且主要的常染色体隐性遗传病见表5-2。 表5-2常染色体隐性遗传病举例 疾病中文名称 疾病英文名称 OMIM 染色体定位 镰状细胞贫血 sickle cell anemia 603903 11p15.5 婴儿黑蒙性白痴 Tay-Sachs disease 272800 15q23-q248 Tay-Sachs 病是神经节苷脂贮积病 GM2中的一种类型，患者由于 基因编码氨基己糖苷酶 A（hexosaminidase A，hexA）α亚单位的基 因突变，酶活性缺失而不能使神经节苷脂降解而堆积所致。 Tay-Sachs Disease Clinical features Severe mental and physical deterioration beginning in infancy, death occurs at age 2 to 3 years. Incidence About 1 in 3600 in Ashkenazi Jewish births; about 1 in 360000 in most other population. Genetics Autosomal recessive Gene location 15q23-q24 Basic defect Mutations at the locus for the α subunit of hexosaminidase A Pathophysiology Deficiency or absence of the lysosomal enzyme hexosaminidase A leads to accumulation of ganglioside GM2 mainly in neurons. Prenantal diagnosis Possible by assay of fetal tissues(including cultured or uncultured amniotic fluid cells or cells of chorionic villi) for activity of the enzyme; also possible by DNA techniques in suitable family Treatment None available Significance Example of a lethal autosomal recessive disorder with high frequency in a specific, genetically isolated population. One of the first disorders for which heterozygote screening was carried out on a large scale, and one of the first metabolic disorders for which prenatal diagnosis was used. 其他一些常见且主要的常染色体隐性遗传病见表 5-2。 表 5-2 常染色体隐性遗传病举例 疾病中文名称 疾病英文名称 OMIM 染色体定位 镰状细胞贫血 sickle cell anemia 603903 11p15.5 婴儿黑蒙性白痴 Tay-Sachs disease 272800 15q23-q24