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目的:对不明原因智力障碍患者进行FMR1基因(CGG)n重复数分析，调查智力障碍患者中脆性X综合征的发病率，进而对患者家系成员进行遗传咨询和产前诊断。方法:本研究募集了201例不明原因智力障碍患者(男173例、女28例)，应用PCR-琼脂糖凝胶电泳(结合FMR1基因RNA表达)、Perkin Elmer FragilEase? PCR-毛细管电泳检测方法对FMR1基因(CGG)n重复数进行分析，并对前突变/全突变携带者孕妇进行产前诊断；同时对智力障碍的全突变携带者女性进行X染色体失活模式检测。结果:在201例不明原因智力障碍患者中共鉴定出15个脆性X综合征全突变家系(先证者为13男2女)，智力障碍患者中脆性X综合征的发病率为7.5%(15/201)。并对6名FMR1基因前突变/全突变携带者孕妇进行了产前诊断。智力障碍全突变携带者女性的X染色体失活模式均为偏斜失活。结论:脆性X综合征在不明原因智力障碍患者中的发病率较高，对不明原因智力障碍患者进行FMR1基因(CGG)n重复数分析，可以为患者及其家系的遗传咨询和产前诊断提供理论依据，FMR1基因分析应作为不明原因智力障碍患者的一线检测手段。“,”Objective:To analyze the (CGG)n repeats of FMR1 gene among patients with unexplained mental retardation.Methods:For 201 patients with unexplained mental retardation, the (CGG)n repeats of the FMR1 gene were analyzed by PCR and FragilEase? PCR. Prenatal diagnosis was provided to carriers of pre- and full-mutations. The pattern of X chromosome inactivation (XCI) was determined for women with mental retardation and full mutations.Results:For the 201 patients with unexplained mental retardation, 15 were identified with full mutations of the FMR1 gene. The prevalence of fragile X syndrome (FXS) in patients with unexplained mental retardation was determined as 7.5%(15/201). Prenatal diagnosis was provided for 6 pregnant women with pre- or full mutations. Analysis revealed that women with mental retardation and full FMR1 mutations exhibited a skewed XCI pattern with primary expression of the X chromosome carrying the mutant allele.Conclusion:FXS has a high incidence among patients with unexplained mental retardation. Analysis of FMR1 gene (CGG)n repeats in patients with unexplained mental retardation can facilitate genetic counseling and prenatal diagnosis for their families. FMR1 gene (CGG)n repeats screening should be recommended for patients with unexplained mental retardation.