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在男性中,脆性X[fra(X)]综合征是智力低下最常见的病因之一,仅次于Down综合征。Turner和Jacobs(1983)对白人男性调查结果,fra(X)综合征流行率约1/2000。Jacobs(1986)对夏威夷调查的结果,未发现fra(X)综合征有明显的种族倾向。本文以前报道的日本男性中fra(X)综合征的频率与白人无显著差异。McKusick认为fra(X)综合征是一种X连锁隐性遗传病,不过与其它所有的人类X连锁疾患有两点不同。第一,fra(X)综合征有时可通过正常男性传递;第二、通过家系研究杂合女性约1/3智力低下。为了确定日本智力低下女性中fra(X)综合征的流行情况,1986年作者对东京以北100公里的Ibaraki等3个收容所中472个智
In men, fragile X [fra (X)] syndrome is one of the most common causes of mental retardation, second only to Down syndrome. Turner and Jacobs (1983) survey of white men, the prevalence of fra (X) syndrome is about 1/2000. The results of the Jacobs (1986) survey of Hawaii found no apparent ethnic bias in fra (X) syndrome. There was no significant difference in frequency of fra (X) syndrome among Japanese men previously reported in this study. McKusick argues that fra (X) syndrome is an X-linked recessive disorder, but differs from all other human X-linked disorders in two ways. First, fra (X) syndrome can sometimes be transmitted by normal males; secondly, about one third of maladies in heterozygous women are studied by pedigree. In order to determine the prevalence of fra (X) syndrome in Japanese women with mental retardation, in 1986, the author evaluated 472 Chileans in three shelters, including Ibaraki, 100 kilometers north of Tokyo