Krishna Murthy D S, Farag T I
Medical Genetics Center, Maternity Hospital, Sulaibikat, Kuwait.
Ann Genet. 1995;38(4):217-24.
Two young, unrelated multiplex families with Bedouin ancestors, each confirmed to have 3 sibs with recurrent regular trisomy-21 are reported. Low grade mosaicism for trisomy-21 (3/350 cells) was confirmed in the mother in one of the families but not in the other. However, two of the relatives (first degree) were confirmed to have Down syndrome. The recurrence risk for trisomy-21 based on livebirth and prenatal diagnosis data were estimated at 1 to 2 percent for couples 35 years old or younger at the time of conception. However, such risk estimates are not available for recurrence of simple trisomy-21 to a particular couple (<35 years). Clustering of trisomy-21, trisomy-18 has been reported among Bedouins. The possibility of cryptic parental mosaicism as well as <
据报道，有两个年轻的、无血缘关系的多成员家庭，其祖先为贝都因人，每个家庭均有3名同胞患有复发性21 -三体综合征。其中一个家庭的母亲被证实存在低水平的21 -三体嵌合体（3/350个细胞），而另一个家庭则未发现。然而，这两个家庭中有两名一级亲属被确诊患有唐氏综合征。根据活产和产前诊断数据，对于受孕时年龄在35岁及以下的夫妇，21 -三体综合征的复发风险估计为1%至2%。然而，对于特定夫妇（年龄小于35岁）单纯性21 -三体综合征复发的此类风险估计尚无数据。在贝都因人中，曾有21 -三体综合征、18 -三体综合征聚集发生的报道。在对有21 -三体综合征或其他非整倍体同胞关系的家庭进行遗传咨询时，应考虑隐匿性父母嵌合体以及<<遗传易感性>>的可能性。
