To investigate the distribution and the characteristics of karyotypes in Down syndrome patients in Nanning city, China, Cytogenetic analysis was carried out in 500 cases clinically suspected for Down syndrome during 1994 to 2007. One hundred and thirty cases were diagnosed as Down syndrome in the panel of patients with karyotyping analysis. The prevalence distribution of chromosome abnormalities in Chinese Down syndrome patients in Nanning were 86.15% (112/130) cases with typical trisomy 21,

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... 6% (11/130) cases with translocation, and 5.39% (7/130) cases with mosaic abnormal karyotype. The cases with trisomy 21 were approximately as twice as higher (1.8:1)in male than that in female patients. The percentage (93.08%) of Down syndrome babies born by younger mothers (<35 yr) was greater than that (6.92%) of the babies born by elder mothers (>35 yr). We concluded that males were more pronounced to be affected than females in Down syndrome cases in Nanning. Down syndrome cases with typical trisomy 21 karyotype were higher in Nanning than those with translocation or mosaic karotypes.