先天愚型又称Down氏综合征。这种疾病虽然人们早有描述,但直到1959年才由Lejeune等人确证此病与染色体异常的因果关系。 现在知道先天愚型有四种类型:21三体型,D/G易位型,G/G易位型和嵌合核型。其中以第一种类型最为常见,约占95％,而两种易位型和嵌合型则很少,各占2.5％左右。这种 Down’s syndrome, also known as Down’s syndrome. Although the disease has long been described, it was not until 1959 that Lejeune et al. Confirmed the causal relationship between the disease and chromosomal abnormalities. Now know that there are four types of Down’s syndrome: trisomy 21, D / G translocation, G / G translocation and chimerism. Among them, the first type is the most common, accounting for about 95%, while the two types of translocation and chimerism are few, each accounting for about 2.5%. This