Psychological characteristics of and counseling for carriers of structural chromosome abnormalities

A Retrospective Analysis of Robertsonian Translocations from a Single Center in China

Robertsonian translocations (ROBs) are the most common structural chromosomal abnormalities in the general population, with an estimated incidence rate of 1/1000 births. In this study, we retrospectively analyzed the cases of ROBs from September 2015 to August 2022 and totally identified ROB carriers from 84,569 specimens karyotyped in a single accredited laboratory in China, including 189 cases of balanced ROBs and 3 of mosaic ROBs. Microsoft Excel and descriptive statistics were used to record and analyze the collected data. The male/female ratio of ROBs is 1/1.29, with der(13;14) and der(14;21) being the main karyotypes. Among the 192 patients, 7 were lost to follow-up, 82 had given birth, and 103 were childless (such as miscarriage, fetal chromosomal abnormalities, in vitro fertilization (IVF) failure, or divorce). A total of 44 amniocenteses were performed in 42 couples; ROB cases with natural pregnancies showed that the normal karyotype and balanced ROBs of fetal accounted for 66.67% (16/24), while the results of assisted pregnancies showed 90.00% (18/20). This study represents the largest collections of ROBs in Jiangxi population and reminder that the ROB carriers can achieve the ideal outcome for pregnancy with the appropriate genetic guidance and assisted reproductive technologies (ART).

Combined use of karyotyping and copy number variation sequencing technology in prenatal diagnosis

Background

Karyotyping and genome copy number variation sequencing (CNV-seq) are two techniques frequently used in prenatal diagnosis. This study aimed to explore the diagnostic potential of using a combination of these two methods in order to provide a more accurate clinical basis for prenatal diagnosis.

Methods

We selected 822 pregnant women undergoing amniocentesis and separated them into six groups according to different risk indicators. Karyotyping and CNV-seq were performed simultaneously to compare the diagnostic performance of the two methods.

Results

Among the different amniocentesis indicators, abnormal fetal ultrasounds accounted for 39.29% of the total number of examinees and made up the largest group. The abnormal detection rate of non-invasive prenatal testing (NIPT) high risk was 37.93% and significantly higher than the other five groups (P < 0.05). The abnormal detection rate of mixed indicators was significantly higher than the history of the adverse reproductive outcomes group (P = 0.0151). The two methods combined found a total of 119 abnormal cases (14.48%). Karyotyping detected 57 cases (6.93%) of abnormal karyotypes, 30 numerical aberrations, and 27 structural aberrations. CNV-seq identified 99 cases (12.04%) with altered CNVs, 30 cases of chromosome aneuploidies, and 69 structural aberrations (28 pathogenic, eight that were likely pathogenic, and 33 microdeletion/duplication variants of uncertain significance (VUS)). Thirty-seven cases were found abnormal by both methods, 20 cases were detected abnormally by karyotyping (mainly mutual translocation and mostly balanced), and 62 cases of microdeletion/duplication were detected by CNV-seq. Steroid sulfatase gene (STS) deletion was identified at chromosome Xp22.31 in three cases. Postnatal follow-up confirmed that babies manifested skin abnormalities one week after birth. Six fetuses had Xp22.31 duplications ranging from 1.5 Kb to 1.7 Mb that were detected by CNV-seq. Follow-up showed that five babies presented no abnormalities during follow-up, except for one terminated pregnancy due to a history of adverse reproductive outcomes.

Conclusion

The combination of using CNV-seq and karyotyping significantly improved the detection rate of fetal pathogenic chromosomal abnormalities. CNV-seq is an effective complement to karyotyping and improves the accuracy of prenatal diagnosis.

Recurrent spontaneous abortion related to balanced translocation of chromosomes: two case reports

Background

Recurrent spontaneous abortion (RSA) is often idiopathic, but structural chromosomal abnormality is an important nosogenesis. Balanced translocations or inversions can lead to unbalanced gametes depending on the specific recombination and segregation patterns during meiosis. An unbalanced karyotype in the conceptus of a couple when one partner has a structural chromosomal abnormality may result in failure to implant, miscarriage, or ongoing pregnancy of a fetus with an unbalanced karyotype.

Case presentation

We report two rare Han cases of RSA associated with balanced translocation of chromosomes. In case 1, a women who had had four spontaneous abortions, the karyotype was 46, XX, t (4;7) (q31;q22). In case 2, a women who had two spontaneous abortions and one stillborn fetus, the karyotype was 46, XX, t (3;15) (q12;p11.2), inv (5) (P13q13). The abnormal karyotype was not found in other chromosomes.

Conclusions

It is very important that couples with more than two miscarriages be provided with chromosomal analysis. Referring couples for karyotyping will rule out or confirm possible hereditary etiology and the source of chromosomal abnormalities in recurrent miscarriages.