Eunpu D L, McDonald D M, Zackai E H
Am J Med Genet. 1986 Oct;25(2):361-3. doi: 10.1002/ajmg.1320250222.
The risk of recurrence for trisomy 21 offspring in couples with one affected child is accepted to be 1%. The rate of trisomy 21 in second- and third-degree relatives is not established. Tamaren et al [Am J Med Genet 15:393-403, 1983] reported a Down syndrome rate of 0.67% among aunts and uncles (second-degree relatives) of a Down syndrome proband. This eightfold rate increase over that for a control group can also be applied to nieces and nephews who are also second-degree relatives. One routinely discusses amniocentesis for lower risk levels; thus, should one offer amniocentesis to every sib of a trisomy 21 proband? We obtained extensive family histories on 141 trisomy 21 kinships to ascertain the rate of trisomy 21 in second-degree relatives. The rate for sibs agreed with the accepted 1% rate. Among aunts and uncles we found no trisomy 21 individuals. We conclude that the rate of trisomy 21 in second-degree relatives does not appear to be sufficiently increased to warrant routine discussion of amniocentesis with sibs of trisomy 21 individuals.
生育过一个患21三体综合征孩子的夫妇，其再次生育21三体综合征患儿的风险被认为是1%。二级和三级亲属中21三体综合征的发生率尚未确定。塔马伦等人[《美国医学遗传学杂志》15:393 - 403，1983年]报告，在21三体综合征先证者的姑姑和叔叔（二级亲属）中，唐氏综合征的发生率为0.67%。与对照组相比，这一发生率高出八倍，同样适用于作为二级亲属的侄女和侄子。人们通常会针对较低风险水平讨论羊膜穿刺术；那么，是否应该为每一位21三体综合征先证者的同胞提供羊膜穿刺术呢？我们获取了141个21三体综合征亲属关系的详尽家族史，以确定二级亲属中21三体综合征的发生率。同胞的发生率与公认的1%相符。在姑姑和叔叔中，我们未发现21三体综合征患者。我们得出结论，二级亲属中21三体综合征的发生率似乎没有显著升高，因此无需与21三体综合征患者的同胞常规讨论羊膜穿刺术。
