Parental risk factors for congenital diaphragmatic hernia - a large German case-control study

Role of genetics and the environment in the etiology of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a congenital malformation characterized by failure of diaphragm closure during embryonic development, leading to pulmonary hypoplasia and pulmonary hypertension, which contribute significantly to morbidity and mortality. The occurrence of CDH and pulmonary hypoplasia is theorized to result from both abnormalities in signaling pathways of smooth muscle cells in pleuroperitoneal folds and mechanical compression by abdominal organs within the chest cavity on the developing lungs. Although, the precise etiology of diaphragm maldevelopment in CDH is not fully understood, it is believed that interplay between genes and the environment contributes to its onset. Approximately 30% of patients with CDH possess chromosomal or single gene defects and these patients tend to have inferior outcomes compared with those without genetic associations. At present, approximately 150 gene variants have been linked to the occurrence of CDH. The variable expression of the CDH phenotype in the presence of a recognized genetic predisposition can be explained by an environmental effect on gene penetrance and expression. The retinoic acid pathway is thought to play an essential role in the interactions of genes and environment in CDH. However, apart from the gradually maturing retinol hypothesis, there is limited evidence implicating other environmental factors in CDH occurrence. This review aims to describe the pathogenesis of CDH by summarizing the genetic defects and potential environmental influences on CDH development.

The etiology of congenital diaphragmatic hernia: the retinoid hypothesis 20 years later

Congenital diaphragmatic hernia (CDH) is a severe birth defect and a major cause of neonatal respiratory distress. Impacting ~2-3 in 10,000 births, CDH is associated with a high mortality rate, and long-term morbidity in survivors. Despite the significant impact of CDH, its etiology remains incompletely understood. In 2003, Greer et al. proposed the Retinoid Hypothesis, stating that the underlying cause of abnormal diaphragm development in CDH was related to altered retinoid signaling. In this review, we provide a comprehensive update to the Retinoid Hypothesis, discussing work published in support of this hypothesis from the past 20 years. This includes reviewing teratogenic and genetic models of CDH, lessons from the human genetics of CDH and epidemiological studies, as well as current gaps in the literature and important areas for future research. The Retinoid Hypothesis is one of the leading hypotheses to explain the etiology of CDH, as we continue to better understand the role of retinoid signaling in diaphragm development, we hope that this information can be used to improve CDH outcomes. IMPACT: This review provides a comprehensive update on the Retinoid Hypothesis, which links abnormal retinoic acid signaling to the etiology of congenital diaphragmatic hernia. The Retinoid Hypothesis was formulated in 2003. Twenty years later, we extensively review the literature in support of this hypothesis from both animal models and humans.

Role of microRNAs in Congenital Diaphragmatic Hernia-Associated Pulmonary Hypertension

Epigenetic regulators such as microRNAs (miRNAs) have a key role in modulating several gene expression pathways and have a role both in lung development and function. One of the main pathogenetic determinants in patients with congenital diaphragmatic hernia (CDH) is pulmonary hypertension (PH), which is directly related to smaller lung size and pulmonary microarchitecture alterations. The aim of this review is to highlight the importance of miRNAs in CDH-related PH and to summarize the results covering this topic in animal and human CDH studies. The focus on epigenetic modulators of CDH-PH offers the opportunity to develop innovative diagnostic tools and novel treatment modalities, and provides a great potential to increase researchers’ understanding of the pathophysiology of CDH.

Seasonal Variation of Congenital Diaphragmatic Hernia: A Review of the Literature and Database Report from the United States and Canada

INTRODUCTION

 The etiology of congenital diaphragmatic hernia (CDH) remains unknown and only 10 to 30% of patients have a genetic cause. Seasonal variation is known to contribute to the development of some congenital anomalies. Our aim was to investigate whether CDH births have seasonal variation.

MATERIALS AND METHODS

 A literature review was conducted for CDH and seasonality. Moreover, data from the CDH International Patient Registry Database were collected for infants with due dates between 2008 and 2014. Due dates were used to determine seasonal distribution of births. Birth rates per month in the United States and Canada were extracted from publicly available databases. Data were analyzed using analysis of variance and contingency tables.

RESULTS

 First, the literature review revealed 11 articles, of which 3 were eligible for inclusion. These studies reported conflicting results on seasonality of CDH. Second, we extracted due dates from the CDH International Patient Registry Database (1,259 patients) and found that there were fewer due dates in winter months (12.1 ± 4 patients/month) than in summer (16.7 ± 6 patients/month; p = 0.011) and fall months (16.3 ± 5 patients/month; p = 0.022). Although this trend was similar to that of all births in the United States and Canada, a lower incidence was observed in winter for CDH infants (20.2%) than for the general population (24.1%, p = 0.0012). CDH survival rate did not vary by season.

CONCLUSION

 This study provides evidence for a seasonal variation of CDH births. No causative link was established between CDH development and seasonality. Population-based studies with a focus on exposome data are needed to explain seasonal variation in CDH.

One Size Does Not Fit All: Congenital Diaphragmatic Hernia Management in Neonates

Congenital diaphragmatic hernia (CDH) results from abnormal development of the diaphragm during fetal life, allowing abdominal organs to herniate through the defect into the thorax. Stunted lung growth is associated with pulmonary hypoplasia and pulmonary hypertension, which are the primary sources of morbidity and mortality for this population. Despite strides in neonatal and surgical care, the management of neonates with CDH remains challenging. Optimal treatment strategies are still largely unknown. Many centers utilize gentle ventilation, permissive hypercapnia, and pulmonary hypertension treatment inclusive of nitric oxide, sildenafil, or epoprostenol, delayed surgical repair, and extracorporeal membrane oxygenation (ECMO). Evidence-based guidelines are needed to enhance CDH care practices and better outcomes. The successful management of CDH is a collaborative team effort from the prenatal to the postnatal period and beyond.

The role of genes and environment in the etiology of congenital diaphragmatic hernias

Structural birth defects are a common cause of abnormalities in newborns. While there are cases of structural birth defects arising due to monogenic defects or environmental exposures, many birth defects are likely caused by a complex interaction between genes and the environment. A structural birth defect with complex etiology is congenital diaphragmatic hernias (CDH), a common and often lethal disruption in diaphragm development. Mutations in more than 150 genes have been implicated in CDH pathogenesis. Although there is generally less evidence for a role for environmental factors in the etiology of CDH, deficiencies in maternal vitamin A and its derivative embryonic retinoic acid are strongly associated with CDH. However, the incomplete penetrance of CDH-implicated genes and environmental factors such as vitamin A deficiency suggest that interactions between genes and environment may be necessary to cause CDH. In this review, we examine the genetic and environmental factors implicated in diaphragm and CDH development. In addition, we evaluate the potential for gene-environment interactions in CDH etiology, focusing on the potential interactions between the CDH-implicated gene, Gata4, and maternal vitamin A deficiency.

The Necessity of Magnetic Resonance Imaging in Congenital Diaphragmatic Hernia

This is a retrospective study investigating the relationship between ultrasound and magnetic resonance imaging (MRI) examinations in congenital diaphragmatic hernia (CDH). CDH is a rare cause of pulmonary hypoplasia that increases the mortality and morbidity of patients. Inclusion criteria were: patients diagnosed with CDH who underwent MRI examination after the second-trimester morphology ultrasound confirmed the presence of CDH. The patients came from three university hospitals in Bucharest, Romania. A total of 22 patients were included in the study after applying the exclusion criteria. By analyzing the total lung volume (TLV) using MRI, and the lung to head ratio (LHR) calculated using MRI and ultrasound, we observed that LHR can severely underestimate the severity of the pulmonary hypoplasia, even showing values close to normal in some cases. This also proves to be statistically relevant if we eliminate certain extreme values. We found significant correlations between the LHR percentage and herniated organs, such as the left and right liver lobes and gallbladder. MRI also provided additional insights, indicating the presence of pericarditis or pleurisy. We wish to underline the necessity of MRI follow-up in all cases of CDH, as the accurate measurement of the TLV is important for future treatment and therapeutic strategy.

Lung to thorax transverse area ratio as a predictor of neurodevelopmental outcomes in fetuses with congenital diaphragmatic hernia

INTRODUCTION

Infants with congenital diaphragmatic hernia (CDH) are at risk of neurodevelopmental disabilities. This study aimed to investigate the association between lung to thorax transverse area ratio (LTR) and neurodevelopmental outcomes at 3 years of age in fetuses with CDH.

METHODS

We performed a retrospective study of infants with prenatally diagnosed isolated left-sided CDH born in Kyushu University Hospital between 2008 and 2016. We examined the association between prenatal ultrasound findings including LTR and development quotient (DQ) at 36 to 42 months of chronological age.

RESULTS

We identified 34 live-born fetuses with isolated left-sided CDH, of which 30 survived and four died before discharge. The median LTR in the survivors was higher than in the non-survivors (p < 0.01). Among the survivors, 26 had available data on LTR (median 0.12, range 0.08-0.18) and overall DQ at 3 years of age (93, 61-112). Their median gestational age and birth weight were 37.6 (range 34.4-39.1) weeks and 2716 (2.256-3494) grams, respectively. There was no significant difference in overall DQ scores between the two groups divided according to the median LTR values (p = 0.62). LTR values were not associated with overall DQ scores after adjusting for gestational age (p = 0.39). In addition, no association was observed between LTR values and any subscale DQ scores.

CONCLUSION

In fetuses with isolated left-sided CDH, prenatal LTR predicts the mortality but not neurodevelopmental outcomes at 3 years of age.

Maternal cigarette smoking and alcohol consumption and congenital diaphragmatic hernia

Background

Congenital diaphragmatic hernia (CDH) occurs when abnormal diaphragm development allows herniation of abdominal organs into the thoracic cavity. Its etiopathogenesis is not well understood, but cigarette smoking and alcohol exposure may impact diaphragm development. Using data from a large, population‐based case–control study, we examined associations between maternal cigarette smoking and alcohol consumption and CDH in offspring.

Methods

We analyzed maternal interview reports of cigarette smoking and alcohol consumption during early pregnancy for 831 children with CDH and 11,416 children without birth defects with estimated dates of delivery during 1997–2011. Generalized linear mixed effects models with a random intercept for study site were used to estimate associations between measures of exposure to smoking (any, type, frequency, duration) and alcohol (any, quantity, frequency, variability, type) for all CDH combined and selected subtypes (Bochdalek and Morgagni).

Results

Mothers of 280 (34.0%) case and 3,451 (30.3%) control children reported early pregnancy exposure to cigarette smoking. Adjusted odds ratios for all CDH were increased for any (1.3; 95% confidence interval 1.1–1.5), active (1.3, 1.0–1.7), and passive (1.4, 1.1–1.7) smoking. Early pregnancy alcohol consumption was reported by mothers of 286 (34.9%) case and 4,200 (37.0%) control children; odds were near the null for any consumption (0.9, 0.8–1.1) and consumption with (0.9, 0.7, 1.1) or without (0.9, 0.8, 1.1) binging. Estimates for smoking and alcohol tended to be higher for Bochdalek CDH and Morgagni CDH than those for all CDH.

Conclusions

Findings suggest that maternal early pregnancy exposure to cigarette smoking, but less so to alcohol consumption, contributes to CDH. These findings need to be replicated in additional large studies that use systematic case ascertainment and classification, detailed exposure assessment, and examine subtype‐specific associations.

Cellular Origin(s) of Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is a structural birth defect characterized by a diaphragmatic defect, lung hypoplasia and structural vascular defects. In spite of recent developments, the pathogenesis of CDH is still poorly understood. CDH is a complex congenital disorder with multifactorial etiology consisting of genetic, cellular and mechanical factors. This review explores the cellular origin of CDH pathogenesis in the diaphragm and lungs and describes recent developments in basic and translational CDH research.

The Role of De Novo Variants in Patients with Congenital Diaphragmatic Hernia

The genetic etiology of congenital diaphragmatic hernia (CDH), a common and severe birth defect, is still incompletely understood. Chromosomal aneuploidies, copy number variations (CNVs), and variants in a large panel of CDH-associated genes, both de novo and inherited, have been described. Due to impaired reproductive fitness, especially of syndromic CDH patients, and still significant mortality rates, the contribution of de novo variants to the genetic background of CDH is assumed to be high. This assumption is supported by the relatively low recurrence rate among siblings. Advantages in high-throughput genome-wide genotyping and sequencing methods have recently facilitated the detection of de novo variants in CDH. This review gives an overview of the known de novo disease-causing variants in CDH patients.

Unraveling the Genetics of Congenital Diaphragmatic Hernia: An Ongoing Challenge

Congenital diaphragmatic hernia (CDH) is a congenital structural anomaly in which the diaphragm has not developed properly. It may occur either as an isolated anomaly or with additional anomalies. It is thought to be a multifactorial disease in which genetic factors could either substantially contribute to or directly result in the developmental defect. Patients with aneuploidies, pathogenic variants or de novo Copy Number Variations (CNVs) impacting specific genes and loci develop CDH typically in the form of a monogenetic syndrome. These patients often have other associated anatomical malformations. In patients without a known monogenetic syndrome, an increased genetic burden of de novo coding variants contributes to disease development. In early years, genetic evaluation was based on karyotyping and SNP-array. Today, genomes are commonly analyzed with next generation sequencing (NGS) based approaches. While more potential pathogenic variants are being detected, analysis of the data presents a bottleneck-largely due to the lack of full appreciation of the functional consequence and/or relevance of the detected variant. The exact heritability of CDH is still unknown. Damaging de novo alterations are associated with the more severe and complex phenotypes and worse clinical outcome. Phenotypic, genetic-and likely mechanistic-variability hampers individual patient diagnosis, short and long-term morbidity prediction and subsequent care strategies. Detailed phenotyping, clinical follow-up at regular intervals and detailed registries are needed to find associations between long-term morbidity, genetic alterations, and clinical parameters. Since CDH is a relatively rare disorder with only a few recurrent changes large cohorts of patients are needed to identify genetic associations. Retrospective whole genome sequencing of historical patient cohorts using will yield valuable data from which today's patients and parents will profit Trio whole genome sequencing has an excellent potential for future re-analysis and data-sharing increasing the chance to provide a genetic diagnosis and predict clinical prognosis. In this review, we explore the pitfalls and challenges in the analysis and interpretation of genetic information, present what is currently known and what still needs further study, and propose strategies to reap the benefits of genetic screening.