Aneuploidy is one of the most important chromosomal aberrations, which involves an abnormal number of the chromosomes. Trisomy 21 (Down syndrome) and numerical aberrations of the sex chromosomes have a relatively high prevalence in the general population. However, the patients usually have one of the above genetic disorders and combined cases of two different trisomies are unusual. We report a case of a patient with double aneuploidy—a combination of trisomy 21 and triple X syndrome. The proband had typical features of Down syndrome and did not manifest any symptoms of polysomy X. The patient had hypotonia, a cardiac defect, and an annular pancreas. A clinical diagnosis of Down syndrome was established, but the cytogenetic analysis found two free full trisomies—trisomy 21 (Down syndrome) and triple X. Cases of double aneuploidy, combining trisomy 21 and trisomy of a sex chromosome, could be challenging because the patients manifest only symptoms, typical for Down syndrome. The discovery of a second complete free trisomy X in our case was an incidental finding. This illustrates the importance of the cytogenetic analysis, despite the evident phenotype of trisomy 21.

中文翻译：

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保加利亚Down表型新生儿双非整倍体48,ХХХ,+21一例

非整倍体是最重要的染色体畸变之一，涉及染色体数量异常。21 三体综合征（唐氏综合症）和性染色体数量畸变在一般人群中的患病率相对较高。然而，患者通常患有上述遗传疾病中的一种，两种不同三体性的合并病例并不常见。我们报告了一例双非整倍体患者——21 三体和三 X 综合征的组合。先证者具有唐氏综合征的典型特征，没有表现出任何 X 多体症的症状。患者有张力减退、心脏缺陷和环状胰腺。唐氏综合征的临床诊断成立，但细胞遗传学分析发现了两个游离的完整三体——21 三体（唐氏综合征）和三重 X。双非整倍体病例，将 21 三体和性染色体三体结合起来可能具有挑战性，因为患者仅表现出唐氏综合症的典型症状。在我们的案例中发现第二个完全游离的 X 三体是一个偶然的发现。这说明了细胞遗传学分析的重要性，尽管 21 三体的表型很明显。