Chromosome 2p (chr2p) duplication, also known as trisomy 2p, is a rare chromosome abnormality associated with developmental delay, intellectual disability, behavioral problems, and distinctive facial features. Most of the reported cases involving trisomy 2p include additional copy number variants (CNVs) in other regions of the genome and are usually small in size. Little is known about the clinical outcomes of large duplications of chr2p as the sole cytogenetic abnormality. In this study, 193 samples at the Greenwood Genetic Center (GGC) with CNVs involving chr2p were evaluated, out of which 86 had chr2p duplications. Among them, 8 patients were identified with large chr2p duplications ranging in size from 9.3 Mb to 89 Mb, and no deletions or duplications involving other chromosomes were identified in those patients. These duplications were associated with inverted duplication, tandem duplication, and duplication as the result of translocation, with no additional CNVs identified by microarray analysis. Confirmation by conventional cytogenetics was performed in 7 of the 8 patients, and the translocations were confirmed by fluorescence in situ hybridization. Interestingly, 1 patient was found to have mosaic complete trisomy 2p as the result of an unbalanced de novo (X;2) chromosomal translocation. X-inactivation was skewed toward the derivative X chromosome, yet it did not appear to extend into the chromosome 2 material. Various shared clinical manifestations were observed in the individuals in this study, including developmental delay, hemifacial hypoplasia, cleft palate, and short stature, and they also have distinct features such as hypotonia, cerebellar hypogenesis, and corpus callosum agenesis, which might result from a gene dosage effect of the duplication. In conclusion, single-event large chr2p duplications can result from different mechanisms, including inverted or tandem duplications within chromosome 2, or translocations involving chromosome 2 and other chromosomes. Partial or complete trisomy 2p is commonly associated with developmental delay, and additional clinical features may be related to gene dosage effects.

中文翻译：

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大染色体 2p 重复相关机制和临床表现。

2p 染色体 (chr2p) 重复，也称为 2p 三体，是一种罕见的染色体异常，与发育迟缓、智力障碍、行为问题和独特的面部特征相关。大多数报道的涉及 2p 三体性的病例在基因组的其他区域都包含额外的拷贝数变异 (CNV)，并且通常较小。对于作为唯一细胞遗传学异常的 chr2p 大量重复的临床结果知之甚少。在这项研究中，对格林伍德遗传中心 (GGC) 的 193 个 CNV 涉及 chr2p 的样本进行了评估，其中 86 个样本存在 chr2p 重复。其中，8名患者被发现存在大小从9.3 Mb到89 Mb的大chr2p重复，并且在这些患者中没有发现涉及其他染色体的缺失或重复。这些重复与反向重复、串联重复和易位导致的重复相关，微阵列分析未发现额外的 CNV。8名患者中的7名进行了常规细胞遗传学证实，并通过荧光原位杂交证实了易位。有趣的是，1 名患者被发现患有马赛克完全三体 2p，这是由于不平衡的从头 (X;2) 染色体易位造成的。X 失活偏向于衍生的 X 染色体，但它似乎并未延伸到 2 号染色体材料中。在本研究中的个体中观察到各种共同的临床表现，包括发育迟缓、半面发育不全、腭裂和身材矮小，并且他们还具有肌张力低下、小脑发育不全和胼胝体发育不全等独特特征，这可能是由于重复的基因剂量效应。总之，单事件大 chr2p 重复可能由不同机制引起，包括 2 号染色体内的反向或串联重复，或涉及 2 号染色体和其他染色体的易位。部分或完全三体 2p 通常与发育迟缓相关，其他临床特征可能与基因剂量效应有关。