Constitutional telomeric associations are very rare events and the mechanism underlying their development is not well understood. We here describe a female case of Turner syndrome with a 45,X,add(22)(p11.2)[25]/45,X[5]. We reconfirmed this karyotype by FISH analysis as 45,X,dic(Y;22)(p11.3;p11.2)[28]/45,X[2].ish dic(Y;22)(SRY+,DYZ1+). A possible mechanism underlying this mosaicism was a loss of dic(Y;22) followed by a monosomy rescue of chromosome 22. However, SNP microarray analysis revealed no loss of heterozygosity (LOH) in chromosome 22, although a mosaic pattern of LOH was clearly detectable at the pseudoautosomal regions of the sex chromosomes. Our results suggest that the separation of the dicentric chromosome at the junction resulted in a loss of chromosome Y without a loss of chromosome 22, leading to this patient’s unique mosaicism. Although telomere signals were not detected by FISH at the junction, it is likely that the original dic(Y;22) chromosome was generated by unstable telomeric associations. We propose a novel “pulled apart” mechanism as the process underlying this mosaicism.

中文翻译：

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与 dic(Y;22) 相关的特纳综合征病例

宪法性端粒关联是非常罕见的事件，其发展的机制尚不清楚。我们在此描述了一例特纳综合征的女性病例，其 45,X,add(22)(p11.2)[25]/45,X[5]。我们通过 FISH 分析再次确认该核型为 45,X,dic(Y;22)(p11.3;p11.2)[28]/45,X[2].ish dic(Y;22)(SRY+,DYZ1+) . 这种镶嵌现象的一个可能机制是 dic(Y;22) 缺失，随后是 22 号染色体的单体性拯救。 然而，SNP 微阵列分析显示 22 号染色体中没有杂合性 (LOH) 缺失，尽管 LOH 的镶嵌模式很明显在性染色体的假常染色体区域可检测到。我们的结果表明，连接处双着丝粒染色体的分离导致 Y 染色体丢失，而 22 号染色体没有丢失，导致该患者独特的镶嵌现象。尽管 FISH 在连接处未检测到端粒信号，但原始 dic(Y;22) 染色体很可能是由不稳定的端粒关联产生的。我们提出了一种新颖的“分离”机制作为这种镶嵌现象的潜在过程。