22q11.2 recurrent copy number variation-related syndrome: a retrospective analysis of our own microarray cohort and a systematic clinical overview of ClinGen curation

Chromosomal abnormalities detected by chromosomal microarray analysis and pregnancy outcomes of 4211 fetuses with high-risk prenatal indications

With the gradual liberalization of the three-child policy and the development of assisted reproductive technology in China, the number of women with high-risk pregnancies is gradually increasing. In this study, 4211 fetuses who underwent chromosomal microarray analysis (CMA) with high-risk prenatal indications were analysed. The results showed that the overall prenatal detection rate of CMA was 11.4% (480/4211), with detection rates of 5.82% (245/4211) for abnormal chromosome numbers and 5.58% (235/4211) for copy number variants. Additionally, the detection rates of clinically significant copy number variants were 3.78% (159/4211) and 1.8% (76/4211) for variants of uncertain significance. The detection rates of fetal chromosomal abnormalities were 6.42% (30/467) for pregnant women with advanced maternal age (AMA), 6.01% (50/832) for high-risk maternal serum screening (MSS) results, 39.09% (224/573) with abnormal non-invasive prenatal testing (NIPT) results, 9.21% (127/1379) with abnormal ultrasound results, and 5.1% (49/960) for other indications. Follow-up results were available for 4211 patients, including 3677 (3677/4211, 87.32%) whose infants were normal after birth, 462 (462/4211, 10.97%) who terminated their pregnancy, 51 (51/4211, 1.21%) whose infants were abnormal after birth, and 21 (21/4211, 0.50%) who refused follow-up. The results of this study demonstrate significant variation in the diagnostic rate of chromosomal microarray analysis across different indications, providing valuable guidance for clinicians to assess the applicability of CMA technology in prenatal diagnosis.

The yield of SNP microarray analysis for fetal ultrasound cardiac abnormalities

BACKGROUND

Chromosomal microarray analysis (CMA) has emerged as a critical instrument in prenatal diagnostic procedures, notably in assessing congenital heart diseases (CHD). Nonetheless, current research focuses solely on CHD, overlooking the necessity for thorough comparative investigations encompassing fetuses with varied structural abnormalities or those without apparent structural anomalies.

OBJECTIVE

This study sought to assess the relation of single nucleotide polymorphism-based chromosomal microarray analysis (SNP-based CMA) in identifying the underlying causes of fetal cardiac ultrasound abnormalities.

METHODS

A total of 2092 pregnant women who underwent prenatal diagnosis from 2017 to 2022 were included in the study and divided into four groups based on the presence of ultrasound structural abnormalities and the specific type of abnormality. The results of the SNP-Array test conducted on amniotic fluid samples from these groups were analyzed.

RESULTS

Findings from the study revealed that the non-isolated CHD group exhibited the highest incidence of aneuploidy, overall chromosomal abnormalities, and trisomy 18, demonstrating statistically significant differences from the other groups (p < 0.001). Regarding the distribution frequency of copy number variation (CNV) segment size, no statistically significant distinctions were observed between the isolated CHD group and the non-isolated CHD group (p > 0.05). The occurrence rates of 22q11.2 and 15q11.2 were also not statistically different between the isolated CHD group and the non-isolated congenital heart defect group (p > 0.05).

CONCLUSION

SNP-based CMA enhances the capacity to detect abnormal CNVs in CHD fetuses, offering valuable insights for diagnosing chromosomal etiology and facilitating genetic counseling. This research contributes to the broader understanding of the utility of SNP-based CMA in the context of fetal cardiac ultrasound abnormalities.

Clinical Experience of Prenatal Chromosomal Microarray Analysis in 6159 Ultrasonically Abnormal Fetuses

A single-center retrospective study of G-band karyotyping and chromosomal microarray analysis (CMA) for the invasive prenatal diagnosis of 6159 fetuses with ultrasound abnormalities was conducted. This study aimed to investigate the incidence rates of chromosomal abnormalities and pregnancy outcomes and postpartum clinical manifestations by long-term follow-up and to explore the correlation between different types of prenatal ultrasound abnormalities and pathogenic chromosomal abnormalities. The overall incidence of pathogenic chromosomal aberrations in fetuses with ultrasound abnormalities was 7.58% (467/6159), which comprised 41.7% (195/467) with chromosome number abnormalities, 57.6% (269/467) with pathogenic copy-number variations (pCNVs), and 0.64% (3/467) with uniparental disomy (UPD). In addition, 1.72% (106/6159) with likely pathogenic copy-number variations (lpCNVs) and 3.04% (187/6159) with variants of unknown significance (VOUS) were detected by CMA. Ultrasound abnormalities were categorized into structural anomalies and soft marker anomalies. The incidence rate of pathogenic and likely pathogenic chromosomal abnormalities was significantly higher among fetuses with structural anomalies than soft markers (11.13% vs 7.59%, p < 0.01). We retrospectively analyzed the prenatal genetic outcomes for a large cohort of fetuses with different types of ultrasound abnormalities. The present study showed that the chromosomal abnormality rate and clinical outcomes of fetuses with different types of ultrasound abnormalities varied greatly. Our data have important implications for prenatal genetic counseling for fetuses with different types of ultrasound abnormalities.

The Subtlety of 22q11.2 Deletion Syndrome in a Preterm Neonate

To date, 22q11.2 deletion syndrome (DS) is regarded as the most commonly diagnosed DS in humans. The location of the deletion on chromosome 22 affects the phenotypic presentation, which ranges from subtle to severe. Common manifestations include congenital heart defects, calcium deficiency, clefts and other midline defects, immunodeficiencies, and neurocognitive delay. This wide range of clinical manifestations can complicate diagnostic reasoning as many align with other disease processes commonly observed in preterm neonates. This article presents the case of a preterm neonate born at 25-weeks' gestation with 22q11.2 DS. The clinical presentation of this neonate included a right aortic arch, ventricular septal defect, hypocalcemia, borderline severe combined immunodeficiency, and abnormal thyroid function. The infant's hospital course is followed to highlight the challenges clinicians face when suspicious of a genetic disorder in a preterm neonate.

Clinical characterization of 72 patients with del(22)(q11.2q11.2) from different ethnic backgrounds

Background

DiGeorge syndrome (DGS), caused by a deletion del(22)(q11.2q11.2), is the most frequently observed microdeletion syndrome. There is a vast clinical heterogeneity in DGS, and several studies suggested also heterogeneity of clinical signs and phenotypic appearance to be related to ethnic differences. Here, clinical characteristics of 72 patients with molecular diagnosed deletion del(22)(q11.2q11.2) derived from different countries from Europe, America, Africa, and Asia are summarized and compared.

Results

Unless ethnic differences, the expected major clinical signs were present in all cases. Frequent clinical manifestations found in this study were congenital heart disease with 68% (49/72), followed by dysmorphic features found in 61% (44/72); neurodevelopmental disorders were present in 43% (31/72) and thymus hypoplasia/aplasia in 32% (23/72). However, clinical features of the patients appeared/were recognized at different times during their lives. Within the group, under 2 years predominated heart disease, dysmorphic features, and hypocalcemia and/or hypoparathyroidism. In the group older than 2 years, the following combination of clinical findings was most frequent: dysmorphic features, congenital heart disease, intellectual disability, and immunological disorders. In the eight cases detected prenatally, abnormal sonographic findings were the major clinical signs (cardiovascular malformations and renal malformations).

Conclusions

Despite the heterogeneous nature of the sample analyzed, a number of clinical findings could be highlighted to be useful for the clinical delineation of this DGS. Interestingly, diagnostic indicators may vary depending on the age at diagnosis. Finally, apparent differences in DGS patients from different regions seem to be rather due to applied test systems than to real differences in patients from different ethnicities.

Different Types of Deletions Created by Low-Copy Repeats Sequences Location in 22q11.2 Deletion Syndrome: Genotype-Phenotype Correlation

The most frequent microdeletion, 22q11.2 deletion syndrome (22q11.2DS), has a wide and variable phenotype that causes difficulties in diagnosis. 22q11.2DS is a contiguous gene syndrome, but due to the existence of several low-copy-number repeat sequences (LCR) it displays a high variety of deletion types: typical deletions LCR A-D-the most common (~90%), proximal deletions LCR A-B, central deletions (LCR B, C-D) and distal deletions (LCR D-E, F).

METHODS

We conducted a retrospective study of 59 22q11.2SD cases, with the aim of highlighting phenotype-genotype correlations. All cases were tested using MLPA combined kits: SALSA MLPA KIT P245 and P250 (MRC Holland).

RESULTS

most cases (76%) presented classic deletion LCR A-D with various severity and phenotypic findings. A total of 14 atypical new deletions were identified: 2 proximal deletions LCR A-B, 1 CES (Cat Eye Syndrome region) to LCR B deletion, 4 nested deletions LCR B-D and 1 LCR C-D, 3 LCR A-E deletions, 1 LCR D-E, and 2 small single gene deletions: delDGCR8 and delTOP3B.

CONCLUSIONS

This study emphasizes the wide phenotypic variety and incomplete penetrance of 22q11.2DS. Our findings contribute to the genotype-phenotype data regarding different types of 22q11.2 deletions and illustrate the usefulness of MLPA combined kits in 22q11.2DS diagnosis.

Case Report: Chinese female patients with a heterozygous pathogenic RPS6KA3 gene variant c.898C>T and distal 22q11.2 microdeletion

Background: Coffin–Lowry syndrome (CLS) [OMIM#303600] is a rare X-linked dominant syndrome. CLS is caused by highly heterogeneous loss-of-function mutations in the RPS6KA3 gene (OMIM*300,075). CLS is characterized by intellectual disability (ID), short stature, tapered fingers, characteristic facial features, and progressive skeletal changes. Distal 22q11.2 microdeletion syndrome (OMIM#611867) is an autosomal dominant and recurrent genomic disorder. It mainly includes three types [distal type I (D–E/F), type II (E–F), and type III (F–G)] and exhibits variable clinical phenotypes (mild, moderate, or even normal): preterm birth, pre- and/or postnatal growth restriction, development delay, ID, behavioral problems, cardiovascular defects, skeletal anomalies, and dysmorphic facial features. We investigated the genetic etiology of a Chinese pedigree with ID, short stature, digit abnormalities, facial dysmorphism, and menstrual disorder. A heterozygous RPS6KA3 gene variant c.898C>T (p.R300X) was identified in this familial case. Two female CLS patients with distal 22q11.2 microdeletion presented with more severe clinical phenotypes. We provided clinical characteristics of these Chinese female CLS patients.

Case presentation: We described a Chinese family with three affected females (the mother, the elder sister, and the proband). The mother and the elder sister had more severe clinical phenotypes (moderate facial dysmorphism, more severe cognitive impairment, and shorter stature). The common characteristic phenotypes are ID, short stature, facial dysmorphism, irregular menstruation, and cardiovascular disorders. Peripheral blood samples were collected from the pedigree. Whole-exome sequencing (WES) identified a heterozygous nonsense RPS6KA3 gene variant c.898C>T (p.R300X). It was verified by Sanger sequencing. Copy number variation sequencing (CNV-seq) showed that both the mother and the elder sister carried a CNVseq [hg19] del (22) (q11.22-q11.23) (22997582–23637176)×0.5. RNA from peripheral blood samples was used for measuring the relative quantification of mRNA (expressed by exon 14 of RPS6KA3). The levels of mRNA relative expressions were significantly lower in the mother’s and the elder sister’s blood samples. The levels of mRNA relative expressions were significantly higher in the proband’s blood sample. X-chromosome inactivation (XCI) studies demonstrated that the proband showed extremely skewed XCI, and the XCI pattern of the elder sister was random.

Conclusion: Herein, we reported three Chinese female patients with a heterozygous nonsense RPS6KA3 gene variant c.898C>T. Further genetic studies were performed. To our knowledge, Chinese patients with this variant have not been previously reported in the literature. The three female patients presented with variable degrees of severity. The clinical characteristics of these Chinese female CLS patients could expand the phenotypic spectrum of CLS. We helped physicians to understand the genotype–phenotype correlation further.

Chromosomal Microarray Analysis in Fetuses Detected with Isolated Cardiovascular Malformation: A Multicenter Study, Systematic Review of the Literature and Meta-Analysis

Cardiovascular malformations (CVM) represent the most common structural anomalies, occurring in 0.7% of live births. The CVM prenatal suspicion should prompt an accurate investigation with fetal echocardiography and the assessment through genetic counseling and testing. In particular, chromosomal microarray analysis (CMA) allows the identification of copy number variations. We performed a systematic review and meta-analysis of the literature, studying the incremental diagnostic yield of CMA in fetal isolated CVM, scoring yields for each category of heart disease, with the aim of guiding genetic counseling and prenatal management. At the same time, we report 59 fetuses with isolated CVM with normal karyotype who underwent CMA. The incremental CMA diagnostic yield in fetuses with isolated CVM was 5.79% (CI 5.54–6.04), with conotruncal malformations showing the higher detection rate (15.93%). The yields for ventricular septal defects and aberrant right subclavian artery were the lowest (2.64% and 0.66%). Other CVM ranged from 4.42% to 6.67%. In the retrospective cohort, the diagnostic yield was consistent with literature data, with an overall CMA diagnostic yield of 3.38%. CMA in the prenatal setting was confirmed as a valuable tool for investigating the causes of fetal cardiovascular malformations.