PDF(Pubmed)
Abstract：
Introduction: Chromosome mosaicism and low-grade mosaicism present a challenge for diagnosis in the era of SNP array and NGS. Tetraploidy is a rare numerical chromosomal abnormality characterized by the presence of four copies of each chromosome. The prevalence of tetraploidy/diploidy mosaicism cases is extremely rare in the human population. Accurate estimates of the frequency of this chromosomal anomaly are lacking due to its classification as an extremely rare and difficult-to-detect condition. Methods: In this report, we describe two cases involving challenging diagnoses of tetraploidy/diploidy and trisomy 12. We utilized advanced genetic testing techniques, including SNP array, to examine the chromosomal abnormalities in these cases. We compared the results from SNP array to conventional G band karyotyping to assess the utility of first-tier prenatal testing methods. Results:Our analysis revealed two cases of tetraploidy/diploidy and trisomy 12 with atypical presentations. SNP array analysis provided higher resolution and more precise information about the chromosomal anomalies in these cases compared to conventional G band karyotyping. Additionally, the prevalence of tetraploidy/diploidy mosaicism was confirmed to be extremely rare in the population. Discussion: Low-level mosaicism is difficult to diagnose, and in many cases, it has traditionally been identified through techniques such as G band karyotype or FISH. Microarray has become an invaluable diagnostic tool for detecting chromosomal abnormalities, offering high-resolution insights. However, it may not always be able to detect rare occurrences of tetraploidy or tetraploidy/diploidy mosaicism. As a result, it is recommended to perform a G band karyotype analysis after obtaining a negative microarray result before considering other diagnostic methods with a potentially higher yield of diagnosis. For the detection of low-level mosaicism, combined diagnostic methods should be considered. The diagnosis of mosaicism is a multistep process that can be time-consuming, often requiring the application of more than one diagnostic technique. This approach is crucial for accurate diagnosis and comprehensive patient care. Further research is warranted to better understand the underlying mechanisms of these rare chromosomal anomalies and to develop more effective diagnostic strategies for challenging cases.
摘要：
简介：染色体镶嵌和低级镶嵌对SNP阵列和NGS时代的诊断提出了挑战。四倍体是一种罕见的染色体异常，其特征是每个染色体存在四个拷贝。在人群中，四倍体/二倍体镶嵌症的患病率极为罕见。由于将其分类为极为罕见且难以检测的条件，因此缺乏对这种染色体异常频率的准确估计。方法：在本报告中，我们描述了两例涉及四倍体/二倍体和12三体的挑战性诊断。我们利用先进的基因检测技术,包括SNP阵列，检查这些病例中的染色体异常。我们将SNP阵列的结果与常规G带核型分析进行了比较，以评估一线产前测试方法的实用性。结果：我们的分析显示2例四倍体/二倍体和三体12，具有非典型表现。与常规G带核型分析相比，SNP阵列分析在这些情况下提供了有关染色体异常的更高分辨率和更精确的信息。此外,四倍体/二倍体镶嵌的患病率被证实在人群中极为罕见.讨论:低水平的镶嵌是很难诊断的,在很多情况下,传统上是通过G带核型或FISH等技术鉴定的。微阵列已成为检测染色体异常的宝贵诊断工具，提供高分辨率的见解。然而,它可能并不总是能够检测到罕见的四倍体或四倍体/二倍体镶嵌现象。因此,我们建议在获得阴性微阵列结果后,进行G带核型分析,然后再考虑其他诊断结果可能较高的诊断方法.对于低水平马赛克的检测，应考虑联合诊断方法。马赛克的诊断是一个多步骤的过程，可能是耗时的，通常需要应用一种以上的诊断技术。这种方法对于准确诊断和全面的患者护理至关重要。需要进一步的研究才能更好地了解这些罕见染色体异常的潜在机制，并为具有挑战性的病例开发更有效的诊断策略。
