Prenatal diagnosis of pure partial monosomy 18p associated with holoprosencephaly and congenital heart defects

A patient with 18p11.32-p11.21 deletion have monaural deafness caused by an inadequate haplodose of THOC1: A case report

BACKGROUND

THOC1 mutation causes Deafness, autosomal dominant 86 [OMIM: 620280]. However, it has not been reported whether deletion of the THOC1 gene causes deafness.

METHODS

Here, we report a 1-year-old girl with clinical features including Hypotonia, unilateral deafness in the right ear, and widening of lateral ventricles in 6 months. Gene mutations were identified by whole-exome sequencing.

RESULTS

Through whole-exome sequencing, a deletion of 18p11.32-p11.21 contains the deletion of all THOC1 genes found in the patient but not in her parents' genomic DNA. The ClinGen Database Haplodose Insufficiency (HI) prediction tool determined that HI, THOC1 HI may cause unilateral deafness. Moreover, after 6 months of rehabilitation training, muscle tone returned to normal. However, at the age of 1 year, the patient developed symptoms of a large liver and hamartoma of both kidneys.

CONCLUSION

From the above results, we propose that in our patient, THOC1 HI may cause unilateral deafness. Therefore, this study provides a new THOC1 deletion associated with unilateral deafness.

Prenatal detection of distal 18p deletion by chromosomal microarray analysis: Three case reports and literature review

BACKGROUND

Chromosome 18p deletion syndrome is caused by total or partial deletion of the short arm of chromosome 18 and associated with cognitive impairment, growth retardation and mild facial dysmorphism. However, most studies on the genotype-phenotype correlations in the 18p region are diagnosed postnatally. Prenatal reports involving 18p deletions are limited.

METHODS

Three pregnant women opted for invasive prenatal testing due to noninvasive prenatal testing indicating high risk for chromosome 18 abnormalities. Karyotypic analysis and chromosomal microarray analysis (CMA) were performed simultaneously. The pregnancy outcomes for all cases were followed up. Meanwhile, we also made a literature review on prenatal phenotypes of 18p deletions.

RESULTS

G-banding analysis showed that 2 fetuses presented abnormal karyotypes: 45,XN,der(18)t(18;21)(p11; q11),-21 (case 2) and 46,XN,18p- (case 3). The karyotype of case 1 was normal. Meanwhile, CMA detected 4.37 Mb (case 1), 7.26 Mb (case 2) and 14.97 Mb (case 3) deletions in chromosome 18p region. All 3 pregnancies were terminated finally according to genetic counseling based upon abnormal CMA results.

CONCLUSION

Prenatal diagnosis of 18p deletion syndrome is full of challenges due to the phenotypic diversity, incomplete penetrance and lack of prenatal phenotypes. Increased nuchal translucency and holoprosencephaly are common prenatal phenotypes of distal 18p deletion. For fetuses carrying 18p deletions with atypical sonographic phenotypes, noninvasive prenatal testing could be adopted as an effective approach.

Prenatal diagnosis of dicentric chromosome X mosaicism: a case report and review

A dicentric chromosome is an abnormal chromosome with two centromeres on the same chromosome. It has been reported that dicentric chromosomes are specific biomarkers of radiation exposure, but dicentric chromosomes are rarely identified in newborns with multiple congenital anomalies. At 16 weeks of gestation, a 39-year-old pregnant woman (gravida 2, para 1) was referred to the prenatal diagnosis center for genetic counseling. The fetal ultrasonography indicated multiple anomalies. Subsequently, amniocentesis was performed, and the G-banding karyotype analysis showed a rare type of mosaicism. The C-banding karyotype analysis indicated a pseudo-dicentric chromosome X [psu dic (X; 18) (p11.2; p11.2)]. A single-nucleotide polymorphism array (SNP array) revealed three pathogenic copy number variations (CNVs). After genetic counseling, the parents chose to terminate this pregnancy. This study provides new evidence for a better understanding of the diagnosis of dicentric chromosomes and emphasizes on the importance of genetic counseling.

The chromosomal characteristics of spontaneous abortion and its potential associated copy number variants and genes

PURPOSE

This study aimed to investigate the correlation between chromosomal abnormalities in spontaneous abortion with clinical features and seek copy number variations (CNVs) and genes that might be connected to spontaneous abortion.

METHODS

Over 7 years, we used CNV-seq and STR analysis to study POCs, comparing chromosomal abnormalities with clinical features and identifying critical CNVs and genes associated with spontaneous abortion.

RESULTS

Total chromosomal variants in the POCs were identified in 66.8% (2169/3247) of all cases, which included 45.2% (1467/3247) numerical abnormalities and 21.6% (702/3247) copy number variants (CNVs). Chromosome number abnormalities, especially aneuploidy abnormalities, were more pronounced in the group of mothers aged ≥ 35 years, the early miscarriage group, and the chorionic villi group. We further analyzed 212 pathogenic and likely pathogenic CNVs in 146 POCs as well as identified 8 statistically significant SORs through comparison with both a healthy population and a group of non-spontaneously aborted fetuses. Our analysis suggests that these CNVs may play a crucial role in spontaneous abortion. Furthermore, by utilizing the RVIS score and MGI database, we identified 86 genes associated with spontaneous abortion, with particular emphasis on PARP6, ISLR, ULK3, FGFRL1, TBC1D14, SCRIB, and PLEC.

CONCLUSION

We found variability in chromosomal abnormalities across clinical features, identifying eight crucial copy number variations (CNVs) and multiple key genes that may be linked to spontaneous abortion. This research enhances the comprehension of genetic factors contributing to spontaneous abortion.

An experience in prenatal diagnosis via QF-PCR of a female child with a 9.9 Mb pure deletion at 18p11.32-11.22

Quantitative Fluorescent - Polymerase Chain Reaction (QF-PCR) is a rapid prenatal diagnosis test for 21, 18, 13 and sex chromosomal aneuploidy detection. However, it could not detect partial trisomy or partial monosomy of those chromosomes. Here, we report a 19-month-old Vietnamese female with a 9.9 Mb pure deletion of chromosome 18 at 18p11.32-11.22 confirmed by next generation sequencing. The patient was short statured with facial dysmorphic features as well as motor skill and speech delays. First trimester screening showed high risk of trisomy 21 with only increased nuchal translucency (NT 3.9 mm) by ultrasound as an indication. Prenatal diagnosis by QF-PCR from amniotic DNA revealed normal disomy. Noticeably, two short tandem repeat (STR) markers D18S391 and D18S976 located on 18p exhibited uninformative patterns (one peak). Thus, our case suggested that the combination of both D18S391 and D18S976 markers with uninformative patterns in QF-PCR for prenatal diagnosis and increased NT in the first trimester ultrasound may be a significant indication of 18p monosomy.

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.

Prenatal ultrasound findings of holoprosencephaly spectrum: Unusual associations

OBJECTIVE

The objective of this study is to evaluate the prenatal diagnosis, postnatal characteristics, and the spectrum of associated findings in fetuses with holoprosencephaly (HPE).

METHODS

Fetal neurosonograms, postnatal assessment, and chromosomal analysis were performed in a cohort of 25 fetuses with HPE.

RESULTS

The prevalence of HPE in high-risk pregnancies was 4.4:10 000. The alobar subtype was the most frequently encountered, with 17 cases (68%). Interestingly, among them, four cases (16%) presented with the rare agnathia-otocephaly complex. Chromosomal abnormalities were detected in 11 cases (44%), the most frequent being trisomy 13 in seven cases (five alobar, one semilobar, and one lobar HPE), followed by trisomy 18 in two cases with semilobar HPE. One case of alobar HPE had 45, XX, t(18;22) (q10;q10), -18p karyotyping, and one case of semilobar HPE was associated with triploidy. Facial malformations in HPE spectrum ranged from cyclopia, proboscis, and arrhinia that were associated with the alobar subtype to hypotelorism and median cleft that were frequent among the semilobar and lobar subtypes. Associated neural tube defects were identified in 12% of cases.

CONCLUSION

Our study illustrates the clinical and genetic heterogeneity of HPE and describes different chromosomal abnormalities associated with HPE.

A case of prenatal diagnosis of 18p deletion syndrome following noninvasive prenatal testing

Background

Chromosome 18p deletion syndrome is a disease caused by the complete or partial deletion of the short arm of chromosome 18, there were few cases reported about the prenatal diagnosis of 18p deletion syndrome. Noninvasive prenatal testing (NIPT) is widely used in the screening of common fetal chromosome aneuploidy. However, the segmental deletions and duplications should also be concerned. Except that some cases had increased nuchal translucency or holoprosencephaly, most of the fetal phenotype of 18p deletion syndrome may not be evident during the pregnancy, 18p deletion syndrome was always accidentally discovered during the prenatal examination.

Case presentations

In our case, we found a pure partial monosomy 18p deletion during the confirmation of the result of NIPT by copy number variation sequencing (CNV-Seq). The result of NIPT suggested that there was a partial or complete deletion of X chromosome. The amniotic fluid karyotype was normal, but result of CNV-Seq indicated a 7.56 Mb deletion on the short arm of chromosome 18 but not in the couple, which means the deletion was de novo deletion. Finally, the parents chose to terminate the pregnancy.

Conclusions

To our knowledge, this is the first case of prenatal diagnosis of 18p deletion syndrome following NIPT.NIPT combined with ultrasound may be a relatively efficient method to screen chromosome microdeletions especially for the 18p deletion syndrome.

Prenatal diagnosis of de novo monosomy 18p deletion syndrome by chromosome microarray analysis: Three case reports

RATIONALE

Monosomy 18p deletion syndrome refers to a rare chromosomal disorder resulting from the part deletion of the short arm of chromosome 18. Prenatal diagnosis of de novo 18p deletion syndrome is a challenge due to its low incidence and untypical prenatal clinical presentation.

PATIENT CONCERNS

Three cases received amniocentesis due to increased nuchal translucency (INT), high risk for Down syndrome, and INT combined intrauterine growth retardation (IUGR), respectively.

DIAGNOSIS

The 3 cases were diagnosed with de novo monosomy 18p deletion syndrome by amniocentesis and chromosome microarray analysis (CMA).

INTERVENTIONS

Karyotype analysis and CMA were used to analyze the abnormal chromosome.

OUTCOMES

Case 1 and case 2 revealed 13.87 and 12.68 Mb deletions by array-CGH analysis, respectively. Case 3 revealed 6.9 Mb deletions in 18p11.32p11.31 and 7.5 Mb deletions in 18p11.23p11.21 by single nucleotide polymorphism array. All of the pregnancies were terminated due to the abnormal chromosome.

LESSONS

The fetal phenotype of monosomy 18p deletion syndrome shows great variability and may not be evident during the pregnancy. CMA may be served as an effective tool for the diagnosis of prenatal monosomy 18p deletion syndrome diagnosis.

A 13-year-old girl with 18p deletion syndrome presenting Turner syndrome-like clinical features of short stature, short webbed neck, low posterior hair line, puffy eyelids and increased carrying angle of the elbows

OBJECTIVE

We report a 13-year-old girl with 18p deletion syndrome presenting Turner syndrome-like clinical features.

CASE REPORT

A 13-year-old girl was referred for genetic counseling of Turner syndrome-like clinical features of short stature, short webbed neck, low posterior hair line, puffy eyelids and increased carrying angle of the elbows. The girl also had mild intellectual disability, psychomotor developmental delay, speech disorder, high-arched palate, hypertelorism and mid-face hypoplasia. Cytogenetic analysis of the girl revealed a karyotype of 46,XX,del(18) (p11.2). The parental karyotypes were normal. Array comparative genomic hybridization analysis on the DNA extracted from the peripheral blood revealed a 13.93-Mb deletion of 18p11.32-p11.21 or arr 18p11.32p11.21 (148,993-14,081,858) × 1.0 [GRCh37 (hg19)] encompassing 52 Online Mendelian Inheritance in Man (OMIM) genes including USP14, TYMS, SMCHD1, TGIF1, LAMA1, TWSG1, GNAL and PTPN2. Polymorphic DNA marker analysis revealed a maternal origin of the deletion.

CONCLUSION

Females with Turner syndrome-like clinical features in association with intellectual disability, facial dysmorphism and psychomotor developmental delay should be suspected of having chromosome deletion syndromes.

Syndromes associated with holoprosencephaly

Holoprosencephaly (HPE) is partial or complete failure of the forebrain to divide into hemispheres and can be an isolated finding or associated with a syndrome. Most cases of HPE are associated with a syndrome and roughly 40%-60% of fetuses with HPE have trisomy 13 which is the most common etiology of HPE. Other syndromes associated with HPE include additional aneuploidies like trisomy 18 and single gene disorders such as Smith-Lemli-Opitz syndrome. There are a number of syndromes such as pseudotrisomy 13 which do not have a known molecular etiology; therefore, this review has two parts: syndromes with a molecular diagnosis and syndromes where the etiology is yet to be found. As most HPE is syndromic, this review provides a comprehensive list and description of syndromes associated with HPE that may be used as a differential diagnosis and starting point for evaluating individuals with HPE.