Neural tube defects and omphalocele in trisomy 18

Prenatal diagnosis of acrania/exencephaly/anencephaly sequence (AEAS): additional structural and genetic anomalies

OBJECTIVES

To analyse additional structural and genetic anomalies in fetuses with acrania/exencephaly/anencephaly sequence (AEAS).

METHODS

A retrospective analysis of 139 fetuses with AEAS diagnosed between 2006 and 2020 in a single tertiary referral ultrasound department.

RESULTS

The median gestational age at diagnosis decreased from 15 weeks in 2006 to 13 weeks in 2020 (- 0.21 per each year; p = 0.009). In 103 fetuses, the defects were limited to the neural tube (NTD) (74.1%), in 36 fetuses (25.9%), there were additional structural non-NTD anomalies. The most common were ventral body wall defects present in 17.8% (23/139), followed by anomalies of the limbs (7.2%; 10/139), face (6.5%; 9/139) and heart (6.5%; 9/139). Genetic anomalies were diagnosed in 7 of the 74 conclusive results (9.5%; 7/74; trisomy 18, n = 5; triploidy, n = 1; duplication of Xq, n = 1). In univariate logistic regression models, male sex, limb anomalies and ventral body wall defects significantly increased the risk of genetic anomalies (OR 12.3; p = 0.024; OR 16.5; p = 0.002 and OR 10.4; p = 0.009, respectively).

CONCLUSIONS

A significant number of fetuses with AEAS have additional structural non-NTD anomalies, which are mostly consistent with limb body wall complex. Genetic abnormalities are diagnosed in almost 10% of affected fetuses and trisomy 18 is the most common aberration. Factors that significantly increased the odds of genetic anomalies in fetuses with AEAS comprise male sex, limb anomalies and ventral body wall defects.

A review of genetic factors underlying craniorachischisis and omphalocele: Inspired by a unique trisomy 18 case

Very few cases of craniorachischisis (CRN) with concomitant omphalocele (OMP) in the setting of trisomy 18 are reported in literature. Solitary midline closure defects are estimated to be more prevalent in trisomy 18 compared to the general population. Neurulation defect comparisons include anencephaly 0-2% versus 0.0206%, spina bifida 1-3% versus 0.0350%, and encephalocele 0-2% versus 0.0082% [Parker et al. (2010); Birth Defects Research. Part A: Clinical and Molecular Teratology, 88:1008-1016; Springett et al. (2015); American Journal of Medical Genetics. Part A, 167A:3062-3069]. The solitary anterior malformation OMP has been reported as high as 6% with trisomy 18 [Springett et al. (2015); American Journal of Medical Genetics. Part A, 167A:3062-3069]. We report the third published case of CRN with concomitant OMP observed in a likely trisomy 18 fetus that screened positive by noninvasive prenatal screening. Furthermore, we review and analyze the current literature to augment understanding of the genetic basis for anterior and posterior closure defects such as CRN and OMP. Although the current genetic lexicon lacks any definitive association with the simultaneous defects presented, previous research elucidated various genes related to anterior or posterior closure interruption individually. By consolidating current research, the authors advance knowledge of interconnected genetic pathology and direct future genetic mapping efforts.

Neural Tube Defects: The Experience of the Registry of Congenital Malformations of Alsace, France, 1995-2009

Context and Objective: Considering the lack of accurate and up-to-date information available about neural tube defects (NTDs) in France, the purpose of this study was to review clinical and epidemiological data of NTDs and to evaluate the current efficiency of prenatal diagnosis in Alsace (northeastern France). Methods: A population-based retrospective study was performed from data of the Registry of Congenital Malformations of Alsace between 1995 and 2009. Data were analyzed as a whole and according to the anatomical type of the malformation (anencephaly, cephalocele and spina bifida). Statistical analyses were carried out using the Statistical Package for the Social Sciences. Results: 272 NTDs were recorded divided in 113 cases of anencephaly (42%), 35 cases of cephalocele (13%) and 124 cases of spina bifida (45%). The total prevalence at birth of 14/10,000 (95% CI 13-16) was stable throughout the reporting period. A chromosome abnormality was identified in 27 cases (12% of all karyotyped cases). NTDs were prenatally diagnosed by ultrasound in 88% of the cases. The mean age upon prenatal diagnosis slightly declined during the 15-year period, significantly for spina bifida only. The global rate of terminations of pregnancy following prenatal diagnosis was 97% (230/238). Conclusion: This work constitutes a unique population-based study providing accurate and specific up-to-date data from a unique center over a longer period (1995-2009). The most important information concerns the high and stable prevalence, which calls into question the efficiency of the primary prevention by folic acid supplementation and the efficiency of prenatal diagnosis.

Craniofacial abnormalities among patients with Edwards Syndrome

OBJECTIVE

To determine the frequency and types of craniofacial abnormalities observed in patients with trisomy 18 or Edwards syndrome (ES).

METHODS

This descriptive and retrospective study of a case series included all patients diagnosed with ES in a Clinical Genetics Service of a reference hospital in Southern Brazil from 1975 to 2008. The results of the karyotypic analysis, along with clinical data, were collected from medical records.

RESULTS:

The sample consisted of 50 patients, of which 66% were female. The median age at first evaluation was 14 days. Regarding the karyotypes, full trisomy of chromosome 18 was the main alteration (90%). Mosaicism was observed in 10%. The main craniofacial abnormalities were: microretrognathia (76%), abnormalities of the ear helix/dysplastic ears (70%), prominent occiput (52%), posteriorly rotated (46%) and low set ears (44%), and short palpebral fissures/blepharophimosis (46%). Other uncommon - but relevant - abnormalities included: microtia (18%), orofacial clefts (12%), preauricular tags (10%), facial palsy (4%), encephalocele (4%), absence of external auditory canal (2%) and asymmetric face (2%). One patient had an initial suspicion of oculo-auriculo-vertebral spectrum (OAVS) or Goldenhar syndrome.

CONCLUSIONS:

Despite the literature description of a characteristic clinical presentation for ES, craniofacial alterations may be variable among these patients. The OAVS findings in this sample are noteworthy. The association of ES with OAVS has been reported once in the literature.

Trisomy 18 and neural tube defects

BACKGROUND

Trisomy 18 or Edwards syndrome is a chromosomal abnormality characterized by a broad clinical picture and a limited survival. More than 130 different abnormalities have been described in these patients-among them are neural tube defects.

METHODS

We verified the frequency and types of major neural tube defects observed among patients with trisomy 18. Our sample consisted of consecutive patients evaluated by a clinical genetics service of a referral hospital in southern Brazil between 1975 and 2008. Fisher's exact test (two-tailed) and chi-square test with Yates' correction were used to compare frequencies (P < 0.05 values were considered as significant).

RESULTS

During the period of evaluation, we identified 50 patients with trisomy 18; 33 (66%) were female and age at the first evaluation ranged from 1 day to 16 years (median 14 days). One cell line with full trisomy 18 was the predominant cytogenetic finding (90%). Three patients (6%) had major neural tube defects, all females. These were two patients (4%) with encephaloceles and one (2%) with myelomeningocele. This last patient undergo to correction surgery on her first day of life.

CONCLUSIONS

Our data, in accordance with the literature, support the idea that the presence of neural tube defects among patients with trisomy 18 is not coincidental (i.e., these defects are actually part of the spectrum of abnormalities presented in trisomy 18). Thus, the diagnosis of trisomy 18 should be considered in children with major neural tube defects, especially in the presence of other abnormalities or dysmorphisms.

Clinical risk factors for gastroschisis and omphalocele in humans: a review of the literature

Gastroschisis and omphalocele are usually considered together since they are both congenital abdominal wall defects, and yet their anatomy, embryogenesis, and clinical presentation and problems are quite different. In addition, it appears that the risk factors for their occurrence differ. Etiologic factors contributing to the development of these defects are unknown. To investigate this we have reviewed reports of risk factors for each anomaly and report them here. We conducted a literature search using PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) for risk factors implicated in the development of gastroschisis and omphalocele. The data reviewed here from clinical studies in the literature, closely parallels the data in animal studies which we reported earlier. There is little evidence for a genetic cause in the development of gastroschisis and much evidence supporting the possibility that environmental teratogens are important contributors to the development of this defect. On the other hand, in the case of omphalocele, there was little evidence for environmental factors and substantial data indicating that genetic or familial factors may play an important role.

Chromosomal abnormalities associated with neural tube defects (I): full aneuploidy

Fetuses with neural tube defects (NTDs) carry a risk of chromosomal abnormalities. The risk varies with maternal age, gestational age at diagnosis, association with other structural abnormalities, and family history of chromosome aberrations. This article provides an overview of chromosomal abnormalities associated with NTDs in embryos, fetuses, and newborn patients, and a comprehensive review of numerical chromosomal abnormalities associated with NTDs, such as trisomy 18, trisomy 13, triploidy, trisomy 9, trisomy 2, trisomy 21, trisomy 7, trisomy 8, trisomy 14, trisomy 15, trisomy 16, trisomy 5 mosaicism, trisomy 11 mosaicism, trisomy 20 mosaicism, monosomy X, and tetraploidy. NTDs may be associated with aneuploidy. Perinatal identification of NTDs should alert one to the possibility of chromosomal abnormalities and prompt a thorough cytogenetic investigation and genetic counseling.

Autosomal dominant nonsyndromic cleft lip and palate: significant evidence of linkage at 18q21.1

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is one of the most common congenital facial defects, with an incidence of 1 in 700-1,000 live births among individuals of European descent. Several linkage and association studies of NSCL/P have suggested numerous candidate genes and genomic regions. A genomewide linkage analysis of a large multigenerational family (UR410) with NSCL/P was performed using a single-nucleotide-polymorphism array. Nonparametric linkage (NPL) analysis provided significant evidence of linkage for marker rs728683 on chromosome 18q21.1 (NPL=43.33 and P=.000061; nonparametric LOD=3.97 and P=.00001). Parametric linkage analysis with a dominant mode of inheritance and reduced penetrance resulted in a maximum LOD score of 3.61 at position 47.4 Mb on chromosome 18q21.1. Haplotype analysis with informative crossovers defined a 5.7-Mb genomic region spanned by proximal marker rs1824683 (42,403,918 bp) and distal marker rs768206 (48,132,862 bp). Thus, a novel genomic region on 18q21.1 was identified that most likely harbors a high-risk variant for NSCL/P in this family; we propose to name this locus "OFC11" (orofacial cleft 11).

Chromosomal abnormalities in fetuses with open neural tube defects: prenatal identification with ultrasound

OBJECTIVES

To determine the prevalence of chromosomal abnormalities in fetuses with open neural tube defects (NTD) undergoing prenatal chromosome analysis. The role of prenatal ultrasound in detecting those with an underlying chromosomal abnormality was also investigated.

METHODS

Over a 6-year period, 144 fetuses with open NTD underwent prenatal chromosome analysis between 12 and 37 weeks of gestation, as part of a prospective, multicenter prenatal diagnosis and counseling program in Chile. This population included 66 fetuses with spina bifida, 46 with acrania/anencephaly, 21 with cephalocele and 11 with iniencephaly. A confident prenatal diagnosis was made in 143 fetuses (99%) and confirmed postnatally in all cases.

RESULTS

An underlying chromosomal abnormality was diagnosed in 10 fetuses (7%), six with spina bifida, three with cephalocele and one with craniorachischisis. The prevalence of chromosomal abnormality varied according to the defect present in the fetus, with a 14% (3/21) prevalence among those with cephalocele, 9% (6/66) among those with spina bifida and 2% (1/57) among those with lethal defects such as acrania, anencephaly or iniencephaly. Karyotype results revealed trisomy 18 in seven cases, trisomy 13 in two and mosaicism for a marker chromosome in one. Prenatal ultrasound before the procedure showed that all chromosomally abnormal fetuses had additional findings. The prevalence of chromosomal abnormality in fetuses with spina bifida and cephalocele was higher when chromosome analysis was performed at or before 24 weeks of gestation in comparison to those performed after 24 weeks (5/31 (16%) vs. 4/56 (7%), respectively). However, this difference did not reach statistical significance, probably due to the small number of cases.

CONCLUSIONS

A significant number of fetuses with open NTD are chromosomally abnormal. Although prenatal chromosome analysis should be considered in all cases, prenatal ultrasound seems effective in identifying those fetuses with an underlying chromosomal abnormality.

Importance of accurate diagnosis in counseling for neural tube defects diagnosed prenatally

In cases of fetal neural tube defects (NTD), termination of pregnancy without ascertainment of specific etiology may lead to provision of incorrect recurrence risks and erroneous diagnosis in future pregnancies. Four patients are presented who illustrate the etiologic diversity of neural tube defects. The patients were referred for prenatal diagnosis because of elevated maternal serum alphafetoprotein (AFP). All four chose pregnancy termination. Diagnostic methods included fetal ultrasound, amniocentesis for fetal karyotyping and amniotic fluid AFP/acetylcholinesterase (AChE) and/or fetal karyotyping after delivery, and dysmorphology evaluation of the fetus after intact delivery. These cases highlight the benefits of fetal karyotype analysis and of an intact delivery and thorough clinical examination of the fetus when patients choose to terminate pregnancies with fetal anomalies.

Neurosonographic abnormalities in chromosomal disorders

A retrospective study of cranial sonograms in infants with autosomal trisomies excluding Down's syndrome was performed. A range of abnormalities was found including structural anomalies, vascular changes and hydrocephalus. Although nonspecific, many of these abnormalities can suggest a specific chromosomal abnormality in the appropriate clinical setting.