A non-syndromic intellectual disability associated with a de novo microdeletion at 7q and 18p, microduplication at Xp, and 18q partial trisomy detected using chromosomal microarray analysis approach

Non-invasive prenatal testing detects duplication abnormalities of fetal chromosome 12

PURPOSE

The 12q terminal duplication is a chromosomal structural abnormality that has been rarely reported. The common clinical manifestations include intellectual disability and speech delay. We report two cases of patients with a duplication of chromosome 12q which was discovered incidentally during non-invasive prenatal genetic testing (NIPT).

METHODS

Next generation sequencing-based NIPT and karyotype analysis confirmed the type and inheritance of the rearrangement, and chromosomal microarray-based analysis also confirmed the end replication.

RESULTS

One patient had a 18Mb 12q24.21q24.33 duplication. The other patient had a12.04Mb12.q24.31q24.33 duplication and a 9.56Mb deletion in 18p11.32p11.22. The duplicated regions on chromosome 12 and the deletion on chromosome 18 in the patients were pathogenic, and the fetuses may have clinical characteristics, such as mental retardation, facial deformities, and psychomotor retardation. Ultimately, both pregnant women chose to terminate their pregnancy.

CONCLUSION

The cases we reported show that NIPT cannot only detect conventional chromosomes, but can also detect microdeletions and microduplications, which broadens the scope of clinical application for NIPT and provides genetic information for high-risk pregnant women as early as possible.

Detection of 21q11.2-q22.11 deletions in a fetus by NIPT

Background

Non‐invasive prenatal testing (NIPT) is extensively used in the detection of fetal trisomies 21, 18, and 13, which is promptly becoming a common clinical practice. Concerned about the clinical application of non‐invasive detection of the fetal autosomal duplications or deletion.

Case Presentation

A 34‐year‐old, healthy pregnant woman was referred to the First Affiliated Hospital of the Air Force Medical University. The ultrasound examination indicates that low‐lying placenta, the fetus has a left ventricular bright spot and small amount of pericardial effusion. NIPT was chosen to further screen for fetal chromosomal abnormalities. NIPT results indicated an approximately 18 Mb deletion, which was verified by prenatal diagnosis. The chromosome microarray analysis (CMA) result showed about 19.2 Mb deletions in 21q11.2‐q22.11. The karyotype analysis result showed 46,XN,del(21)(q11.2q22.1). Prenatal diagnosis was consistent with NIPT results, and the paternal karyotype revealed no obvious abnormalities.

Conclusion

In this study, we successfully detected and diagnosed deletions of large fragments in chromosome 21 in a fetus using NIPT. This indicates that NIPT can provide effective genetic information for detecting fetal subchromosomal deletions/duplications.

A foetus with 18p11.32-q21.2 duplication and Xp22.33-p11.1 deletion derived from a maternal reciprocal translocation t(X;18)(q13;q21.3)

BACKGROUND

Non-invasive prenatal testing (NIPT) evaluates circulating cell-free DNA (cfDNA) and has been widely applied, with highly accurate results for detecting foetal trisomies 21, 18 and 13. Recently, increasing attention has been paid to the clinical application of the non-invasive detection of foetal sub-chromosomal duplications and deletions beyond common aneuploidies.

CASE PRESENTATION

A 32-year-old healthy pregnant woman was referred to the Medical Genetic Centre of Ganzhou Maternal and Child Health Care Hospital. As routine practice, ultrasound examination at a gestational age of 16 weeks showed that the foetus is normal. To avoid invasive prenatal diagnosis procedures, an NIPT was offered to further screen for common foetal chromosomal abnormalities. The result showed that there was an approximately 50.94 Mb duplication in p11.32-q21.2 of chromosome 18 and an approximately 58.46 Mb deletion in p22.33-p11.1 of chromosome X. In addition, the chromosome karyotypes of the parents and foetus were also analysed. Chromosome karyotype analysis results showed that foetal karyotype was 46,X,der(18), the maternal karyotype was 46,XX,t(X;18)(q13;q21.3), and the paternal karyotype revealed no obvious abnormality.

CONCLUSION

In this case, we successfully detected a healthy pregnant woman with balanced translocation X;18(q13;q21.3) and described the foetal karyotype as 46,X,der(18)t(X;18)(q11;q21.1)mat. Our report illustrated these cases which present complex X;autosome balance translocation and X;autosome unbalance translocation which may contribute to severe clinical phenotypes. In addition, our report also proved that the interruption of genes in the Xq critical region is not only reason of primary infertility. Finally, we prompted that NIPT might play a role in the first trimester screening of sub-chromosomal rearrangement.

Application of an improved targeted next generation sequencing method to diagnose non‑syndromic mental retardation in one step: A case report

The genetic basis of congenital mental retardation includes chromosomal anomalies and single gene mutations. In addition to chromosome microarray analysis, next‑generation sequencing (NGS) and Sanger sequencing have additionally been applied to identify single gene mutations. However, no methods exist to identify the cause of an anomaly in one step. The present study applied an improved targeted NGS method to diagnose an 8‑year‑old Chinese Han female with mental retardation in one step. The microdeletion 17p11.2 was successfully detected by the improved targeted NGS and no single gene mutations were identified. The same microdeletion was verified using low coverage whole‑genome sequencing. Fertility guidance was also given to the patient's parents. In the present study, an improved targeted NGS method was applied to diagnose non‑syndromic mental retardation of unknown cause in one step. This improved method has the potential to be developed into a screening panel for the effective diagnosis of genetic abnormalities in non‑syndromic mental retardation and other congenital anomalies.

[Cochlear implantation in a girl with 7q-microdeletion syndrome]

One of the rare genetic diseases with sensory hearing loss is the microdeletion 7q syndrome. First described in the 1990s, only 7 cases of patients with this disease are described in the literature. Although this mutation is not well known, otological treatment is necessary if the DFNA5 gene is affected. A mutation in this gene leads to progressive hearing loss. Affected children therefore need regular evaluation of their hearing to ensure adequate treatment with hearing aids at early stages. We now present a case of an affected child with sensory hearing loss, mental retardation and anogenital malformations. In the following we describe the course of disease and possible treatment options. We especially describe the possibility of cochlear implantation. We can show with this case report that, even though massive mental retardation is shown, cochlear implantation is useful in this patient. Associated disabilities as cardiac and pulmonary problems may occur and should be treated before cochlear implantation. This is the first report of cochlear implantation in a child affected with microdeletion 7q syndrome.