Down′s综合征存在倒置的小嵌合核型

Upended micro-mosaic karyotype in Down′s syndrome existed.

目的观察正常细胞核型中含有极少量21-三体细胞的患儿临床表型及发育损害的相关关系。方法外周血淋巴细胞培养，常规染色体制片，G分带，计数30个细胞分裂相，有临床指征提示时加数至50-100个，计算正常细胞与21-三体细胞之间的比例。结果经过细胞核型与临床比对，发现正常细胞与21-三体细胞之间的比例在10-20：1时，患儿仍然具有Down综合征面容，诊断不困难。而如果这种比例在25-40：1时，患儿则可能完全不具备面容特征，但可出现生长发育落后，脑损害等（简称为倒置的21-三体小嵌合核型）。结论明确Down综合征存在倒置的小嵌合核型。对临床病因诊断，评估21-三体细胞携带者生育风险及其在Down流行病学上的作用都具有重要意义。

Objective： A few trisomy 21 cells in normal chromosome karyotype was been observed for study of the correlation of clinical phenotype and development damage in sick children of Downs syndrome： Methods： Lymphocytes in peripheral blood was culturod , chromosome and G band was routinely prepared, 30 cell division phase as well as the rate of the normal and trisomy 21 cells were calculated. If clinic menifeatation demonstrated as Down＇s sign, 50- 100 cells were Counted. Results： The Lab test of chromo- some karyotype compared with clinic appearance indicates that children with Down＇s faces when the rate of the normal and tirsomy 21 cells is 10 -20： 1. If the rate is 25 -40：1 those children with the upended micro - mosaic trisomy 21 karyotype may be not demonstrated as Down＇s appearance but they have backward development and brain damage. Conclusion： The observation proves that children with Down＇s syndrome exist upended micro - mosaic trisomy 21 karyotype and it pays important role in clinic diagnosis and birth risk evaluation of tiresomy 21 cell carriers as well as epidemic investigation .