Mosaic trisomy 12 diagnosed in a female patient: clinical features, genetic analysis, and review of the literature

Artificial intelligence for prenatal chromosome analysis

This review article delves into the rapidly advancing domain of prenatal diagnostics, with a primary focus on the detection and management of chromosomal abnormalities such as trisomy 13 ("Patau syndrome)", "trisomy 18 (Edwards syndrome)", and "trisomy 21 (Down syndrome)". The objective of the study is to examine the utilization and effectiveness of novel computational methodologies, such as "machine learning (ML)", "deep learning (DL)", and data analysis, in enhancing the detection rates and accuracy of these prenatal conditions. The contribution of the article lies in its comprehensive examination of advancements in "Non-Invasive Prenatal Testing (NIPT)", prenatal screening, genomics, and medical imaging. It highlights the potential of these techniques for prenatal diagnosis and the contributions of ML and DL to these advancements. It highlights the application of ensemble models and transfer learning to improving model performance, especially with limited datasets. This also delves into optimal feature selection and fusion of high-dimensional features, underscoring the need for future research in these areas. The review finds that ML and DL have substantially improved the detection and management of prenatal conditions, despite limitations such as small sample sizes and issues related to model generalizability. It recognizes the promising results achieved through the use of ensemble models and transfer learning in prenatal diagnostics. The review also notes the increased importance of feature selection and high-dimensional feature fusion in the development and training of predictive models. The findings underline the crucial role of AI and machine learning techniques in early detection and improved therapeutic strategies in prenatal diagnostics, highlighting a pressing need for further research in this area.

Challenging diagnoses of tetraploidy/diploidy and trisomy 12: utility of first-tier prenatal testing methods

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.

Rare structural variants, aneuploidies, and mosaicism in individuals with Mullerian aplasia detected by optical genome mapping

The molecular basis of Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome remains largely unknown. Pathogenic variants in WNT4 and HNF1B have been confirmed in a small percent of individuals. A variety of copy number variants have been reported, but causal gene(s) remain to be identified. We hypothesized that rare structural variants (SVs) would be present in some individuals with MRKH, which could explain the genetic basis of the syndrome. Large molecular weight DNA was extracted from lymphoblastoid cells from 87 individuals with MRKH and available parents. Optical genome mapping (OGM) was performed to identify SVs, which were confirmed by another method (quantitative PCR, chromosomal microarray, karyotype, or fluorescent in situ hybridization) when possible. Thirty-four SVs that overlapped coding regions of genes with potential involvement in MRKH were identified, 14 of which were confirmed by a second method. These 14 SVs were present in 17/87 (19.5%) of probands with MRKH and included seven deletions, three duplications, one new translocation in 5/50 cells-t(7;14)(q32;q32), confirmation of a previously identified translocation-t(3;16)(p22.3;p13.3), and two aneuploidies. Of interest, three cases of mosaicism (3.4% of probands) were identified-25% mosaicism for trisomy 12, 45,X(75%)/46,XX (25%), and 10% mosaicism for a 7;14 translocation. Our study constitutes the first systematic investigation of SVs by OGM in individuals with MRKH. We propose that OGM is a promising method that enables a comprehensive investigation of a variety of SVs in a single assay including cryptic translocations and mosaic aneuploidies. These observations suggest that mosaicism could play a role in the genesis of MRKH.

Pigmentary mosaicism as a recurrent clinical manifestation in three new patients with mosaic trisomy 12 diagnosed postnatally: cases report and literature review

Background

To date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases.

Case presentation

In the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50–100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12.

Conclusions

The detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue.