Objective To investigate the distribution of the abnormal karyotype in mental retardation /developmental delay (MR/DD) children of Chongqing to provide the information for diagnosis and genetic counseling. Methods The samples of the peripheral blood lymphocytes from 1743 children were prepared with routine cytogenetic methods,G-banding was employed for karyotype analysis. Results A total of 742 patients(42. 57%) were identified to have abnormalities with 20 kinds of karyotypes. Down s syndrome was the most common in euchromosome malformation, and Klinefelter syndrome in sex chromosome malformation. 80. 69% were found abnormalities in Down s syndrome group, which were coincided with clinical diagnosis and the most of 870 cases were infants;2. 08% were detected in Fragile X syndrome group and major subjects were preschool children;57. 12% in Cri-du-chat syndrome group;4. 95% in MR/DD with non-dysmorphic group,major of 626 cases were 3-5 years old,respectively. Conclusion The most abnormal karyotypes of MR/DD children are Down's,Klinefelter and Fragile X syndrome in Chongqing. It is suggested that more chromosomal information of MR/DD should be acquired,it benefits for early management and intervention of genetic diseases.%目的 了解重庆地区智力低下/发育迟缓儿童染色体异常的主要分布情况,为疾病的病因诊断、遗传咨询提供理论依据.方法 对1743例儿童无菌外周血进行常规接种、培养、制片及G带分析.结果 1743例中检出基因异常共742例,异常检出率42.57%,异常核型共20种,常染色体异常以21-三体综合征为主,性染色体异常以Klinefelter综合征为主.按送检病因分类染色体检出异常相符情况为21-三体综合征80.69%,送检年龄集中在小于1岁组;脆性X综合征2.08%,送检年龄主要是3~5岁儿童;猫叫综合征57.12%(4/7);表型不易识别智力低下/发育迟缓4.95%,送检儿童年龄大部分为3~5岁.结论 重庆地区智力低下/发育迟缓儿童最常见染色体异常为Down′s 综合征、Kilinefelter综合征、脆性X综合征.临床上应较全面获取智力低下/发育迟缓儿童的染色体信息,以利于疾病的早期干预和管理.
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