本文报告40例具有典型外貌21-三体综合征的患儿,并全部经染色体核型(G带)证实;其中男22例,女18例,三体型36例占94.7%;嵌合型2例占5.3%;未发现易位型.并存症:(1)伴发Hb COSP综合征1例,其父母、哥哥均符合α一地中海贫血特征.先天愚型为常染色体畸变的遗传病; This article reports 40 cases of children with typical appearance of 21-trisomy syndrome, and all confirmed by chromosome karyotype (G band), including 22 males and 18 females, trisomy 36 cases accounted for 94.7%; chimerism 2 Cases accounted for 5.3%; no translocation type was found. Complications: (1) 1 case of Hb COSP syndrome, whose parents and elder brothers were consistent with α-thalassemia characteristics. Down’s syndrome is a genetic disorder of autosomal dominant;