Department of Neurology, Dalian Municipal Friendship Hospital, Dalian, PR China.
Clin Genet. 2013 Jul;84(1):74-7. doi: 10.1111/cge.12026. Epub 2012 Oct 17.
The grey zone (GZ; 45-54 CGG repeats in the FMR1 gene) is considered a normal allele; however, several studies have found a high frequency of GZ in movement disordered populations. Here, we describe neurological features of fragile X-associated tremor/ataxia syndrome (FXTAS) in two carriers of GZ alleles, although FXTAS has been defined as occurring only in premutation carriers (55-200 CGG repeats). Both patients had family members who had premutation and were diagnosed with FXTAS. The presence of relatively high GZ alleles with elevated fragile X mental retardation 1 mRNA (FMR1-mRNA) combined with a family history of FXTAS that may represent a facilitating genetic background for FXTAS are the factors that led to the presence of FXTAS in these individuals with a GZ allele. Further research into clinical involvement of GZ alleles is recommended and the definition of FXTAS may require revision.
灰区（GZ；FMR1 基因中 45-54 个 CGG 重复）被认为是正常等位基因；然而，多项研究发现运动障碍人群中 GZ 的频率较高。在这里，我们描述了两位 GZ 等位基因携带者的脆性 X 相关震颤/共济失调综合征（FXTAS）的神经特征，尽管 FXTAS 仅被定义为发生在前突变携带者（55-200 CGG 重复）中。两位患者都有前突变的家族成员，并被诊断为 FXTAS。存在相对较高的 GZ 等位基因，伴有脆性 X 智力低下 1 信使 RNA（FMR1-mRNA）升高，加上 FXTAS 的家族史，可能代表了 FXTAS 的促进遗传背景，这些因素导致了这些 GZ 等位基因个体出现 FXTAS。建议进一步研究 GZ 等位基因的临床参与，并且 FXTAS 的定义可能需要修订。
