Abstract
BackgroundConstitutional telomeric associations are very rare events and the mechanism underlying their development is not well understood.Case presentationWe 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.ConclusionsOur 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.
Highlights
IntroductionConstitutional telomeric associations are very rare events and the mechanism underlying their development is not well understood
Constitutional telomeric associations are very rare events and the mechanism underlying their development is not well understood.Case presentation: We here describe a female case of Turner syndrome with a 45,X,add(22)(p11.2)[25]/45,X[5]
SNP microarray analysis revealed no loss of heterozygosity (LOH) in chromosome 22, a mosaic pattern of LOH was clearly detectable at the pseudoautosomal regions of the sex chromosomes
Summary
Constitutional telomeric associations are very rare events and the mechanism underlying their development is not well understood. Case presentation: 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+). The loss of telomere function can lead to dicentric chromosomes as a result of end-to-end fusions, a phenomenon referred to as telomeric associations (TAs) [1]. About 10 cases of TAs between two autosomal chromosomes have been reported to date, all preferentially involving acrocentric chromosomes. Cases with TAs involving an autosome and chromosome Y have been occasionally reported. Cases of constitutional TAs between an autosome and Kawamura et al Mol Cytogenet (2021) 14:34
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