Congenital diaphragmatic hernia: is 15q26.1-26.2 a candidate locus?

Prenatal Sonographic Features of Ring Chromosome 15: A Case Report and Literature Review

Ring chromosome 15, a rare genetic disease, is very rarely prenatally diagnosed. We present a unique case of fetal ring chromosome 15 with ultrasound findings at 32 weeks of gestation including congenital diaphragmatic hernia, hypoplasia of the aorta with persistent left SVC, growth restriction, clubfeet and scoliosis. We also performed an analytical literature review of prenatal sonographic findings of the disease. This review suggests that ring chromosome 15 has a relatively specific sonographic pattern that could facilitate early detection. The specific sonographic features of ring chromosome 15 include fetal growth restriction, congenital diaphragmatic hernia, abnormal limb postures, cardiac defects, low-set ears and other less frequent, non-specific anomalies that can be identified in more than 50% of cases.

Genetic Diagnostic Strategies and Counseling for Families Affected by Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is a relatively common and severe birth defect with variable clinical outcome and associated malformations in up to 60% of patients. Mortality and morbidity remain high despite advances in pre-, intra-, and postnatal management. We review the current literature and give an overview about the genetics of CDH to provide guidelines for clinicians with respect to genetic diagnostics and counseling for families. Until recently, the common practice was (molecular) karyotyping or chromosome microarray if the CDH diagnosis is made prenatally with a 10% diagnostic yield. Undiagnosed patients can be reflexed to trio exome/genome sequencing with an additional diagnostic yield of 10 to 20%. Even with a genetic diagnosis, there can be a range of clinical outcomes. All families with a child with CDH with or without additional malformations should be offered genetic counseling and testing in a family-based trio approach.

Expanding the clinical spectrum of pathogenic variation in NR2F2: Asplenia

We present a case with congenital syndromic asplenia associated with immune deficiency, glandular hypospadias and cryptorchidism. Genetic analysis identified a likely pathogenic de novo variant in NR2F2. Pathogenic NR2F2 variants have been associated with other congenital anomalies affecting the central axis, such as congenital heart disease and diaphragmatic hernia, which were not part of our patient's clinical features. The association between NR2F2 and asplenia (including glandular hypospadias and cryptorchidism) has been described in animal models and our report is the first expanding the NR2F2 clinical spectrum in humans to include asplenia.

15q26 deletion in a patient with congenital heart defect, growth restriction and intellectual disability: case report and literature review

Background

15q26 deletion is a relatively rare chromosomal disorder, and it is described only in few cases. Patients with this aberration show many signs and symptoms, particularly pre- and postnatal growth restriction, developmental delay, microcephaly, intellectual disability and various congenital malformations.

Case presentation

We report on a girl, 4 years old, of consanguineous parents, with a 15q26 deletion. Clinical manifestations included failure to thrive, developmental delay, microcephaly, dysmorphic facies with broad forehead, hypertelorism, narrowed eyelid slits and protruding columella. The patient also showed skeletal abnormalities, especially clinodactyly of the 5th finger, varus equine right foot and left club foot. Additionally, she had teething delay and divergent strabismus. Heart ultrasound displayed two atrial septal defects with left-to-right shunt, enlarging the right cavities. Routine cytogenetic analysis revealed a shortened 15q chromosome. Subsequent array analysis disclosed a terminal 9.15 Mb deletion at subband 15q26.1-q26.3. Four candidate genes associated with 15q26 deletion phenotype were within the deleted region, i.e. IGF1R, NR2F2, CHD2 and MEF2A.

Conclusion

We report on an additional case of 15q26 monosomy, characterized by array-CGH. Molecular cytogenetic analysis allowed us to identify the exact size of the deletion, and four candidate genes for genotype-phenotype correlation. 15q26 monosomy should be considered when growth retardation is associated with hearing anomalies and congenital heart defect, especially atrioventricular septal defects (AVSDs) and/or aortic arch anomaly (AAA).

CHD2-Related CNS Pathologies

Epileptic encephalopathies (EE) are severe epilepsy syndromes characterized by multiple seizure types, developmental delay and even regression. This class of disorders are increasingly being identified as resulting from de novo genetic mutations including many identified mutations in the family of chromodomain helicase DNA binding (CHD) proteins. In particular, several de novo pathogenic mutations have been identified in the gene encoding chromodomain helicase DNA binding protein 2 (CHD2), a member of the sucrose nonfermenting (SNF-2) protein family of epigenetic regulators. These mutations in the CHD2 gene are causative of early onset epileptic encephalopathy, abnormal brain function, and intellectual disability. Our understanding of the mechanisms by which modification or loss of CHD2 cause this condition remains poorly understood. Here, we review what is known and still to be elucidated as regards the structure and function of CHD2 and how its dysregulation leads to a highly variable range of phenotypic presentations.

The influence of genetics in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common birth defect that is associated with significant morbidity and mortality, especially when associated with additional congenital anomalies. Both environmental and genetic factors are thought to contribute to CDH. The genetic contributions to CDH are highly heterogeneous and incompletely defined. No one genetic cause accounts for more than 1-2% of CDH cases. In this review, we summarize the known genetic causes of CDH from chromosomal anomalies to individual genes. Both de novo and inherited variants contribute to CDH. Genes causing CDH are increasingly identified from animal models and from genomic strategies including exome and genome sequencing in humans. CDH genes are often transcription factors, genes involved in cell migration or the components of extracellular matrix. We provide clinical genetic testing strategies in the clinical evaluation that can identify a genetic cause in up to ∼30% of patients with non-isolated CDH and can be useful to refine prognosis, identify associated medical and neurodevelopmental issues to address, and inform family planning options.

Phenotypic Features and Response to GH Treatment of Patients With a Molecular Defect of the IGF-1 Receptor

CONTEXT

The phenotype and response to GH treatment of children with an IGF1R defect is insufficiently known.

OBJECTIVE

To develop a clinical score for selecting children with short stature for genetic testing and evaluate the efficacy of treatment.

DESIGN AND SETTING

Case series with an IGF1R defect identified in a university genetic laboratory.

PATIENTS AND INTERVENTIONS

Of all patients with sufficient clinical data, 18 had (likely) pathogenic mutations (group 1) and 7 had 15q deletions including IGF1R (group 2); 19 patients were treated with GH.

MAIN OUTCOME MEASURES

Phenotype and response to GH treatment.

RESULTS

In groups 1 and 2, mean (range) birth weight, length, and head circumference (HC) SD scores (SDSs) were -2.1 (-3.7 to -0.4), -2.7 (-5.0 to -1.0), and -1.6 (-3.0 to 0.0), respectively. At presentation, height, HC, and serum IGF-1 SDSs were -3.0 (-5.5 to -1.7), -2.5 (-4.2 to -0.5), and +1.2 (-1.3 to 3.2), respectively. Feeding problems were reported in 15 of 19 patients. A clinical score with 76% sensitivity is proposed. After 3 years of GH treatment [1.1 (0.2) mg/m2/d] height gain in groups 1 (n = 12) and 2 (n = 7) was 0.9 SDS and 1.3 SDS (at a mean IGF-1 of 3.5 SDS), less than reported for small for gestational age (1.8 SDS).

CONCLUSION

A clinical score encompassing birth weight and/or length, short stature, microcephaly, and IGF-1 is useful for selecting patients for IGF1R analysis. Feeding problems are common and the growth response to GH treatment is moderate.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

Response to Growth Hormone Treatment in a Patient with Insulin-Like Growth Factor 1 Receptor Deletion

We report a six-year-old boy who presented with short stature, microcephaly, dysmorphic features, and developmental delay and who was identified with a terminal deletion of 15q26.2q26.3 containing the insulin-like growth factor receptor (IGF1R) gene in addition to a terminal duplication of the 4q35.1q35.2 region. We compare our case with other reports of deletions and mutations affecting the IGF1R gene associated with pre-and postnatal growth restriction. We report the dramatic response to growth hormone therapy in this patient which highlights the importance of identifying patients with IGF1R deletion and treating them early.

Chromosome 15 structural abnormalities: effect on IGF1R gene expression and function

Insulin-like growth factor 1 receptor (IGF1R), mapping on the 15q26.3 chromosome, is required for normal embryonic and postnatal growth. The aim of the present study was to evaluate the IGF1R gene expression and function in three unrelated patients with chromosome 15 structural abnormalities. We report two male patients with the smallest 15q26.3 chromosome duplication described so far, and a female patient with ring chromosome 15 syndrome. Patient one, with a 568 kb pure duplication, had overgrowth, developmental delay, mental and psychomotor retardation, obesity, cryptorchidism, borderline low testis volume, severe oligoasthenoteratozoospermia and gynecomastia. We found a 1.8-fold increase in the IGF1R mRNA and a 1.3-fold increase in the IGF1R protein expression (P < 0.05). Patient two, with a 650 kb impure duplication, showed overgrowth, developmental delay, mild mental retardation, precocious puberty, low testicular volume and severe oligoasthenoteratozoospermia. The IGF1R mRNA and protein expression was similar to that of the control. Patient three, with a 46,XX r(15) (p10q26.2) karyotype, displayed intrauterine growth retardation, developmental delay, mental and psychomotor retardation. We found a <0.5-fold decrease in the IGF1R mRNA expression and an undetectable IGF1R activity. After reviewing the previously 96 published cases of chromosome 15q duplication, we found that neurological disorders, congenital cardiac defects, typical facial traits and gonadal abnormalities are the prominent features in patients with chromosome 15q duplication. Interestingly, patients with 15q deletion syndrome display similar features. We speculate that both the increased and decreased IGF1R gene expression may play a role in the etiology of neurological and gonadal disorders.

Congenital diaphragmatic hernias: from genes to mechanisms to therapies

Congenital diaphragmatic hernias (CDHs) and structural anomalies of the diaphragm are a common class of congenital birth defects that are associated with significant morbidity and mortality due to associated pulmonary hypoplasia, pulmonary hypertension and heart failure. In ∼30% of CDH patients, genomic analyses have identified a range of genetic defects, including chromosomal anomalies, copy number variants and sequence variants. The affected genes identified in CDH patients include transcription factors, such as GATA4, ZFPM2, NR2F2 and WT1, and signaling pathway components, including members of the retinoic acid pathway. Mutations in these genes affect diaphragm development and can have pleiotropic effects on pulmonary and cardiac development. New therapies, including fetal endoscopic tracheal occlusion and prenatal transplacental fetal treatments, aim to normalize lung development and pulmonary vascular tone to prevent and treat lung hypoplasia and pulmonary hypertension, respectively. Studies of the association between particular genetic mutations and clinical outcomes should allow us to better understand the origin of this birth defect and to improve our ability to predict and identify patients most likely to benefit from specialized treatment strategies.

Abnormal Paraventricular Nucleus of Hypothalamus and Growth Retardation Associated with Loss of Nuclear Receptor Gene COUP-TFII

The paraventricular nucleus of hypothalamus plays important roles in the regulation of energy balance and fetal growth. However, the molecular mechanisms underlying its formation and function have not been clearly elucidated. Various mutations in the human COUP-TFII gene, which encodes a nuclear receptor, result in growth retardation, congenital diaphragmatic hernia and congenital heart defects. Here, we show that COUP-TFII gene is expressed in the developing hypothalamus in mouse. The ventral forebrain-specific RXCre/+; COUP-TFII^F/F mutant mice display growth retardation. The development of the paraventricular nucleus of hypothalamus is compromised in the COUP-TFII mutant mainly because of increased apoptosis and mis-migration of the Brn2⁺ neurons. Moreover, hypoplastic anterior pituitary with blood cell clusters and shrunken posterior pituitary lacking AVP/OT neuron innervations are observed in the mutant, indicating the failure of formation of the hypothalamic-pituitary axis. Mechanistic studies show that the expression of Bdnf and Nrp1 genes is reduced in the mutant embryo, and that Bdnf is a direct downstream target of the COUP-TFII protein. Thus, our findings provide a novel functional validation that COUP-TFII gene promotes the expression of Bdnf and Nrp1 genes to ensure the appropriate morphogenesis of the hypothalamic-pituitary axis, especially the paraventricular nucleus of hypothalamus, and to prevent growth retardation.

Expanding the clinical spectrum of chromosome 15q26 terminal deletions associated with IGF-1 resistance

Haploinsufficiency of the insulin-like growth factor-1 receptor (IGF1R) gene on chromosome 15q26.3 is associated with impaired prenatal and postnatal growth, developmental delay, dysmorphic features and skeletal abnormalities. Terminal deletions of chromosome 15q26 arising more proximally may also be associated with congenital heart disease, epilepsy, diaphragmatic hernia and renal anomalies. We report three additional cases of 15q26 terminal deletions with novel features which may further expand the spectrum of this rarely reported contiguous gene syndrome. Phenotypic features including neonatal lymphedema, aplasia cutis congenita and aortic root dilatation have not been reported previously. Similarly, laboratory features of insulin-like growth factor 1 (IGF-1) resistance are described, including markedly elevated IGF-1 of up to +4.7 SDS. In one patient, the elevated IGF-1 declined over time and this coincided with a period of spontaneous growth acceleration.

CONCLUSION

Deletions of 15q26 are a potential risk factor for aortic root dilatation, neonatal lymphedema and aplasia cutis in addition to causing growth restriction. What is Known: • Terminal deletions of chromosome 15q26 are associated with impaired prenatal and postnatal growth, developmental delay, dysmorphic features and skeletal abnormalities. What is New: • Neonatal lymphedema, aplasia cutis congenita and aortic root dilatation have not been previously described in 15q26 terminal deletions and may represent novel features. • IGF-1 levels may be increased up to 4.7 SDS.

De novo frameshift mutation in COUP-TFII (NR2F2) in human congenital diaphragmatic hernia

COUP-TFII (NR2F2) is mapped to the 15q26 deletion hotspot associated with the common and highly morbid congenital diaphragmatic hernia (CDH). Conditional homozygous deletions of COUP-TFII in mice result in diaphragmatic defects analogous to the human Bochdalek-type hernia phenotype. Despite evidence from animal models however, mutations in the coding sequence of COUP-TFII have not been reported in patients, prompting the speculation that additional coding or non-coding sequences in the 15q26 locus are necessary for diaphragmatic hernias to develop. In this report, we describe a case of a patient with a heterozygous de novo COUP-TFII frameshift mutation, presenting with CDH and an atrial septal defect. The p.Pro33AlafsTer77 mutation specifically disrupts protein isoform 1 which contains the DNA binding domain. In addition, we review other COUP-TFII sequence variations and deletions that have been described in cases of CDH. We conclude that COUP-TFII mutations can cause diaphragmatic hernias, and should be included in the differential diagnosis of CDH patients, particularly those with comorbid congenital heart defects. © 2016 Wiley Periodicals, Inc.

Recombinant Human Growth Hormone Therapy in Children with Chromosome 15q26 Deletion

BACKGROUND

The insulin-like growth factor 1 receptor (IGF IR) gene is located on chromosome 15q26.3. Heterozygous 15q26 deletions involving the IGFIR gene are rare, resulting in intrauterine and postnatal growth retardation, developmental delay and microcephaly. Limited evidence exists on the effect of growth hormone (GH) therapy in these cases.

METHODS

We report a series of cases with 15q26 deletions, including response to GH treatment.

RESULTS

Seven children (2 males) presented with short stature [median height standard deviation score (SDS) of -4.8 (range -3.0 to -5.6)]. GH was started at a median age of 5 years (range 1.8 to 12.4) for a median duration of 5.8 years (range 1.0 to 12.4). Median height SDS increased by +0.6 (range 0.1 to 1.0), +1.3 (range 0.1 to 2.4) and +1.4 (range 0.8 to 3.3) after 1 (n = 7), 5 (n = 4) and 10 years (n = 3) of GH treatment, respectively. Four patients reached final height after 5.8 to 12.4 years of GH with a median change in height SDS of +1.1 (range 0 to 3.3).

CONCLUSION

This study demonstrates a moderate, though variable, response to GH therapy, suggesting that GH resistance caused by heterozygous IGFIR deletions can be partially overcome by GH therapy. The first-year response was moderate, and whilst long-term treatment improved height SDS, the final adult height remained reduced. Therefore, an individual trial of GH therapy may be appropriate in these patients. © 2015 S. Karger AG, Basel.

Prenatal diagnosis of a fetus with ring chromosomal 15 by two- and three-dimensional ultrasonography

We report on a prenatal diagnosis of ring chromosome 15 in a fetus with left congenital diaphragmatic hernia (CDH) and severe intrauterine growth restriction (IUGR). A 31-year-old woman, gravida 2 para 1, was referred because of increased nuchal translucency at gestational age of 13 weeks. Comprehensive fetal ultrasound examination was performed at 19 weeks revealing an early onset IUGR, left CDH with liver herniation, and hypoplastic nasal bone. Three-dimensional ultrasound (rendering mode) showed low set ears and depressed nasal bridge. Amniocentesis was performed with a result of a 46,XX,r(15) fetus after a cytogenetic study. A 1,430 g infant (less than third percentile) was born at 36 weeks. The infant presented with respiratory failure and died at 2 h of life. Postnatal karyotype from the umbilical cord confirmed the diagnosis of 15-ring chromosome. We described the main prenatal 2D- and 3D-ultrasound findings associated with ring chromosome 15. The interest in reporting the present case is that CDH can be associated with the diagnosis of 15-ring chromosome because the critical location of the normal diaphragm development is at chromosome 15q26.1-q26.2.

Characterization of a 520 kb deletion on chromosome 15q26.1 including ST8SIA2 in a patient with behavioral disturbance, autism spectrum disorder, and epilepsy

We present a patient with a behavioral disorder, epilepsy, and autism spectrum disorder who has a 520 kb chromosomal deletion at 15q26.1 encompassing three genes: ST8SIA2, C15orf32, and FAM174B. Alpha-2,8-Sialyltransferase 2 (ST8SIA2) is expressed in the developing brain and appears to play an important role in neuronal migration, axon guidance and synaptic plasticity. It has recently been implicated in a genome wide association study as a potential factor underlying autism, and has also been implicated in the pathogenesis of bipolar disorder and schizophrenia. This case provides supportive evidence that ST8SIA2 haploinsufficiency may play a role in neurobehavioral phenotypes.

De novo copy number variants are associated with congenital diaphragmatic hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a common birth defect with significant morbidity and mortality. Although the aetiology of CDH remains poorly understood, studies from animal models and patients with CDH suggest that genetic factors play an important role in the development of CDH. Chromosomal anomalies have been reported in CDH.

METHODS

In this study, the authors investigated the frequency of chromosomal anomalies and copy number variants (CNVs) in 256 parent-child trios of CDH using clinical conventional cytogenetic and microarray analysis. The authors also selected a set of CDH related training genes to prioritise the genes in those segmental aneuploidies and identified the genes and gene sets that may contribute to the aetiology of CDH.

RESULTS

The authors identified chromosomal anomalies in 16 patients (6.3%) of the series including three aneuploidies, two unbalanced translocation, and 11 patients with de novo CNVs ranging in size from 95 kb to 104.6 Mb. The authors prioritised the genes in the CNV segments and identified KCNA2, LMNA, CACNA1S, MYOG, HLX, LBR, AGT, GATA4, SOX7, HYLS1, FOXC1, FOXF2, PDGFA, FGF6, COL4A1, COL4A2, HOMER2, BNC1, BID, and TBX1 as genes that may be involved in diaphragm development. Gene enrichment analysis identified the most relevant gene ontology categories as those involved in tissue development (p=4.4×10(-11)) or regulation of multicellular organismal processes (p=2.8×10(-10)) and 'receptor binding' (p=8.7×10(-14)) and 'DNA binding transcription factor activity' (p=4.4×10(-10)).

CONCLUSIONS

The present findings support the role of chromosomal anomalies in CDH and provide a set of candidate genes including FOXC1, FOXF2, PDGFA, FGF6, COL4A1, COL4A2, SOX7, BNC1, BID, and TBX1 for further analysis in CDH.

Congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is defined by the presence of an orifice in the diaphragm, more often left and posterolateral that permits the herniation of abdominal contents into the thorax. The lungs are hypoplastic and have abnormal vessels that cause respiratory insufficiency and persistent pulmonary hypertension with high mortality. About one third of cases have cardiovascular malformations and lesser proportions have skeletal, neural, genitourinary, gastrointestinal or other defects. CDH can be a component of Pallister-Killian, Fryns, Ghersoni-Baruch, WAGR, Denys-Drash, Brachman-De Lange, Donnai-Barrow or Wolf-Hirschhorn syndromes. Some chromosomal anomalies involve CDH as well. The incidence is < 5 in 10,000 live-births. The etiology is unknown although clinical, genetic and experimental evidence points to disturbances in the retinoid-signaling pathway during organogenesis. Antenatal diagnosis is often made and this allows prenatal management (open correction of the hernia in the past and reversible fetoscopic tracheal obstruction nowadays) that may be indicated in cases with severe lung hypoplasia and grim prognosis. Treatment after birth requires all the refinements of critical care including extracorporeal membrane oxygenation prior to surgical correction. The best hospital series report 80% survival but it remains around 50% in population-based studies. Chronic respiratory tract disease, neurodevelopmental problems, neurosensorial hearing loss and gastroesophageal reflux are common problems in survivors. Much more research on several aspects of this severe condition is warranted.

Microdeletion of chromosome 15q26.1 in a child with intractable generalized epilepsy

Chromosomal abnormalities involving deletions and duplications are known to cause severe developmental disorders, including mental retardation, dysmorphism, and seizures, in children. As the technique of array-based comparative genomic hybridization is being applied more frequently in the diagnostic evaluation of children with developmental disorders, novel pathologic chromosomal abnormalities are being identified. We report the case of a 9-year-old girl with a history of pervasive developmental disorder, growth delay, mild dysmorphic features, and intractable primary generalized epilepsy with a de novo microdeletion of approximately 0.73-0.94 Mb within chromosome 15q26.1. A much larger (5 Mb) but overlapping microdeletion has been previously reported in a 30-month-old child with similar phenotype including intractable myoclonic epilepsy, growth delay, and dysmorphic features. This leads us to propose that a potential candidate gene or genes within the deleted region involved in the pathogenesis of some forms of generalized intractable epilepsy, previously considered to be idiopathic.

Two short children born small for gestational age with insulin-like growth factor 1 receptor haploinsufficiency illustrate the heterogeneity of its phenotype

CONTEXT

Small for gestational age (SGA)-born children comprise a heterogeneous group in which only few genetic causes have been identified.

OBJECTIVE

To determine copy number variations in 18 growth-related genes in 100 SGA children with persistent short stature.

METHODS

Copy number variations in 18 growth-related genes (SHOX, GH1, GHR, IGF1, IGF1R, IGF2, IGFBP1-6, NSD1, GRB10, STAT5B, ALS, SOCS2, and SOCS3) were determined by an "in house" multiplex ligation-dependent probe amplification kit. The deletions were further characterized by single-nucleotide polymorphism array analysis.

RESULTS

Two heterozygous de novo insulin-like growth factor 1 receptor (IGF1R) deletions were found: a deletion of the complete IGF1R gene (15q26.3, exons 1-21), including distally flanking sequences, and a deletion comprising exons 3-21, extending further into the telomeric region. In one case, serum IGF-I was low (-2.78 sd score), probably because of a coexisting growth hormone (GH) deficiency. Both children increased their height during GH treatment (1 mg/m(2) per day). Functional studies in skin fibroblast cultures demonstrated similar levels of IGF1R autophosphorylation and a reduced activation of protein kinase B/Akt upon a challenge with IGF-I in comparison with controls.

CONCLUSIONS

IGF1R haploinsufficiency was present in 2 of 100 short SGA children. GH therapy resulted in moderate catch-up growth in our patients. A review of the literature shows that small birth size, short stature, small head size, relatively high IGF-I levels, developmental delay, and micrognathia are the main predictors for an IGF1R deletion.

The etiology of congenital diaphragmatic hernia: still largely unknown?

Congenital diaphragmatic hernia (CDH) is a severe birth defect characterized by a defect in the diaphragm associated with pulmonary hypoplasia and postnatal pulmonary hypertension. Half of the cases present with other non-pulmonary congenital anomalies (so called non-isolated CDH) and in 5-10% of cases there is a chromosomal etiology. The clinical aspects of CDH are well documented but knowledge on the etiology of CDH is largely lacking. Worldwide many researchers have focused research efforts on CDH. Their findings have led to several hypotheses proposing roles for genetic and environmental factors. In this review we have combined these findings with our own research on the genetics of CDH in results from recent literature and propose a theory on the etiology of CDH. We also propose a protocol for the CDH patient that will help clinicians and researchers to obtain maximal success out of their collaborations that will eventually lead to unravelling the etiology of this intriguing birth defect.

Early onset myoclonic epilepsy and 15q26 microdeletion: observation of the first case

The authors report the study of a 30-month-old girl with refractory myoclonic epilepsy associated with mental retardation, growth delay, peculiar facial appearance, and minor physical anomalies. Extensive genetic studies were performed, including an array-based comparative genomic hybridization (array-CGH) that showed a cryptic interstitial deletion of 15q (5 Mb) affecting the 15q26.1-26.2 region. Partial deletions of the long arm of chromosome 15, including the 15q26 region, were observed in syndromic associations that typically include congenital diaphragmatic hernia, but neurologic features were poorly described and epileptic seizures were never reported. Our findings suggest that genes for seizures could be included in the 15q26.1q26.2 deletion interval.

Drayer's syndrome of mental retardation, microcephaly, short stature and absent phalanges is caused by a recurrent deletion of chromosome 15(q26.2-->qter)

We reevaluated a unique family with two sibs who had a presumed autosomal recessively inherited syndrome characterized by mental retardation, microcephaly, short stature and absent phalanges. This family was originally described by Drayer et al. in 1977. Using modern molecular techniques, we demonstrated that the syndrome is caused by the recurrence of an apparently de novo 15qter deletion of 5.8 Mb. Analysis of polymorphic markers revealed that the deletion was of maternal origin in both cases, indicating germline mosaicism in the clinically unaffected mother. This study demonstrates the possibility of parental mosaicism and the risk of recurrence in sibs for terminal subtelomeric deletions.

Successful long-term growth hormone therapy in a girl with haploinsufficiency of the insulin-like growth factor-I receptor due to a terminal 15q26.2->qter deletion detected by multiplex ligation probe amplification

CONTEXT

Microscopically visible heterozygous terminal 15q deletions encompassing the IGF1R gene are rare and usually associated with intrauterine growth retardation and short stature. The incidence of submicroscopic deletions is unknown, as is the effect of GH therapy in this condition.

OBJECTIVE

The objective of the study was to describe the use of a novel genetic technique [multiplex ligation probe amplification (MLPA)] to detect haploinsufficiency of the IGF1R gene in a patient suspected of an IGF1R gene defect and evaluate the effect of long-term GH therapy.

PATIENT

A 15-yr-old adolescent, born small for gestational age, showed persistent postnatal growth retardation, microcephaly, and elevated IGF-I levels. She had been treated with GH since the age of 5 yr.

METHODS

MLPA and array comparative genomic hybridization (aCGH) were performed to examine gene copy number changes. Dermal fibroblast cultures were used for functional analysis.

RESULTS

With MLPA, a deletion of one copy of the IGF1R gene was detected, defined by aCGH as a loss of 15q26.2->qter. IGF1R mRNA expression was decreased in fibroblasts. IGF-I binding and type 1 IGF receptor protein expression as well as activation of type 1 IGF receptor autophosphorylation and protein kinase B/Akt by IGF-I tended to be lower, but this did not reach statistical significance. GH treatment resulted in a good growth response and a normal adult height.

CONCLUSIONS

MLPA and aCGH are useful tools to detect submicroscopic deletions of the IGF1R gene in patients born small for gestational age with persistent growth failure. The phenotype resembles that of a heterozygous inactivating IGF1R mutation. Long-term GH therapy causes growth acceleration in childhood and a normal adult height.

Array based characterization of a terminal deletion involving chromosome subband 15q26.2: an emerging syndrome associated with growth retardation, cardiac defects and developmental delay

Background

Subtelomeric regions are gene rich and deletions in these chromosomal segments have been demonstrated to account for approximately 2.5% of patients displaying mental retardation with or without association of dysmorphic features. However, cases that report de novo terminal deletions on chromosome arm 15q are rare.

Methods

In this study we present the first example of a detailed molecular genetic mapping of a de novo deletion in involving 15q26.2-qter, caused by the formation of a dicentric chromosome 15, using metaphase FISH and tiling resolution (32 k) genome-wide array-based comparative genomic hybridization (CGH).

Results

After an initial characterization of the dicentric chromosome by metaphase FISH, array CGH analysis mapped the terminal deletion to encompass a 6.48 megabase (Mb) region, ranging from 93.86–100.34 Mb on chromosome 15.

Conclusion

In conclusion, we present an additional case to the growing family of reported cases with 15q26-deletion, thoroughly characterized at the molecular cytogenetic level. In the deleted regions, four candidate genes responsible for the phenotype of the patient could be delineated: IGFR1, MEF2A, CHSY1, and TM2D3. Further characterization of additional patients harboring similar 15q-aberrations might hopefully in the future lead to the description of a clear cut clinically recognizable syndrome.

Congenital diaphragmatic hernia

The incidence of congenital diaphragmatic hernia (CDH) may be as high as 1 in 2000. Over the past two decades, antenatal diagnosis rates have increased, the pathophysiology of CDH has become better understood, and advances in clinical care, including foetal surgery, have occurred. However, there remains a paucity of randomised controlled trials to provide evidence-based management guidelines. Reports of improved survival rates appear to be confined to a select subset of CDH infants, surviving to surgical repair, while the overall mortality, at over 60%, appears to be unchanged, largely due to the often forgotten 'hidden mortality' of CDH. The significant long-term morbidity in surviving infants has become apparent, and the need for long-term multidisciplinary follow up established. A total of 10% of cases may present later in life, and misdiagnosis on initial chest X-ray may lead to significant morbidity.

Congenital diaphragmatic hernia, etiology and management, a 10-year analysis of a single center

OBJECTIVE

To analyze congenital diaphragmatic hernia (CDH) during a 10-year period at the University of Kiel, from 1995 through 2004, in order to develop a strategy to improve prenatal diagnosis, to be able to consider endoscopical treatment for selected cases and to assess the current postnatal treatment strategies.

METHODS

Data were obtained from the fetal medicine ultrasound department, from the birth registry, from the postmortem registry, from the neonatal intensive care unit, from pediatric surgery and from the genetic database. Data were subselected for chromosomes, genetic syndromes, for isolated CDH and for associated anomalies, the lung to head ratio and lung volumes were assessed. Data were analyzed respectively for gestation at diagnosis, the type of CDH, the perinatal management and the postnatal outcome.

RESULTS

There were 29 cases of CDH, in 10/29 (34%) the parents requested termination of pregnancy of which two had already died during pregnancy, 12/19 (63%) survived, which was defined as discharge from the neonatal intensive care unit, seven newborns 7/19 (37%) died in the hospital, 5 of these 5/7 (71%) were delivered in Kiel. A prenatal diagnosis was performed in 16/29 (55%), 1/16 (6%), 7/16 (43%) and 8/16 (50%) in the 1st, 2nd and 3rd trimester, respectively; in 10/29 (34%) diagnosis was performed postpartum, in 3/29 (10%) the diagnosis was performed at autopsy following termination of pregnancy. When the liver was in the abdomen, 9/10 (90%) of the children survived, compared to only 3/8 (43%) when the liver was located in the thorax. A lung to head ratio of 0.81 at 24 weeks resulted in death due to pulmonary hypoplasia.

CONCLUSIONS

The overall survival in CDH is around 50%, antenatal endoscopical therapy may only be considered, if the diagnosis is performed in the early second trimester, and selection criteria such as the lung to head ratio, associated defects and the chromosomal status can be applied.

Congenital diaphragmatic hernia (CDH) etiology as revealed by pathway genetics

Congenital diaphragmatic hernia (CDH) is a common birth defect with high mortality and morbidity. Two hundred seventy CDH patients were ascertained, carefully phenotyped, and classified as isolated (diaphragm defects alone) or complex (with additional anomalies) cases. We established different strategies to reveal CDH-critical chromosome loci and genes in humans. Candidate genes for sequencing analyses were selected from CDH animal models, genetic intervals of recurrent chromosomal aberration in humans, such as 15q26.1-q26.2 or 1q41-q42.12, as well as genes in the retinoic acid and related pathways and those known to be involved in embryonic lung development. For instance, FOG2, GATA4, and COUP-TFII are all needed for both normal diaphragm and lung development and are likely all in the same genetic and molecular pathway. Linkage analysis was applied first in a large inbred family and then in four multiplex families with Donnai-Barrow syndrome (DBS) associated with CDH. 10K SNP chip and microsatellite markers revealed a DBS locus on chromosome 2q23.3-q31.1. We applied array-based comparative genomic hybridization (aCGH) techniques to over 30, mostly complex, CDH patients and found a de novo microdeletion in a patient with Fryns syndrome related to CDH. Fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) techniques allowed us to further define the deletion interval. Our aim is to identify genetic intervals and, in those, to prioritize genes that might reveal molecular pathways, mutations in any step of which, might contribute to the same phenotype. More important, the elucidation of pathways may ultimately provide clues to treatment strategies.

Molecular characterization of a ring chromosome 15 in a fetus with intra uterine growth retardation and diaphragmatic hernia

OBJECTIVE

To improve the phenotype-genotype correlation in terminal 15q deletions and ring chromosome 15 syndrome.

METHODS

Echographic examination of fetus. R-banded chromosome and FISH analysis on cultured amniocytes. Microsatellite analysis to determine parental origin of the ring chromosome 15. Fetal autopsy.

RESULTS

We report a new case of prenatal diagnosis of congenital diaphragmatic hernia and intrauterine growth retardation in a fetus with ring chromosome 15 involving 15q26.1-qter deletion.

CONCLUSION

This case support the evidence that the region 15q26.3 is implicated in intrauterine growth retardation and suggests that the 15q critical region implicated in congenital diaphragmatic hernia is localized in 15q26.1-q26.2.

Overview of epidemiology, genetics, birth defects, and chromosome abnormalities associated with CDH

Congenital diaphragmatic hernia (CDH) is a common and well-studied birth defect. The etiology of most cases remains unknown but increasing evidence points to genetic causation. The data supporting genetic etiologies which are detailed below include the association of CDH with recurring chromosome abnormalities, the existence of CDH-multiplex families, and the co-occurrence of CDH with additional congenital malformations.

Genetic factors in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a relatively common birth defect associated with high mortality and morbidity. Although the exact etiology of most cases of CDH remains unknown, there is a growing body of evidence that genetic factors play an important role in the development of CDH. In this review, we examine key findings that are likely to form the basis for future research in this field. Specific topics include a short overview of normal and abnormal diaphragm development, a discussion of syndromic forms of CDH, a detailed review of chromosomal regions recurrently altered in CDH, a description of the retinoid hypothesis of CDH, and evidence of the roles of specific genes in the development of CDH.

Experiences in the Perinatal Management of Congenital Diaphragmatic Hernia during the Last 15 Years in a Tertiary Referral Institute

OBJECTIVE

Review of cases of perinatally diagnosed congenital diaphragmatic hernias with special regard to time of diagnosis, organs herniated into the thorax, associated malformations, and outcomes.

METHODS

We analyzed the data of 106 cases between July 1, 1990, and June 30, 2005. The observation period was analyzed in two parts.

RESULTS

Prenatal ultrasound was performed in 89.6% (95/106) of the cases. 51.7% (46/89) of the pre- and postnatally verified congenital diaphragmatic hernia cases were diagnosed before the 24th week of gestation. 11% (11/100) of the hernias were identified postnatally. 71% (71/100) of the cases were associated with other malformations. The hernia was on the left side in 86% (86/100) and bilateral in 5% (5/100) of the cases. Between 1990 and 1997, the proportion of right-sided hernias was 4.3% (2/46), while during the second period it was 13% (7/54). 27.5% (14/51) of the newborns survived the perinatal period. The survival rate of the newborns delivered by caesarean section was three times higher than that of infants delivered vaginally. In the latter group, the rate of premature deliveries was considerably higher. The pregnancy was terminated in 45% (40/89) of the cases. 15% (6/40) of the terminated cases were isolated. Intrauterine or intrapartum deaths occurred in 5.6% (5/89) of the prenatally diagnosed cases. Simultaneous thoracic herniation of liver, spleen, or stomach decreased the survival rate. In these cases, the discharge rate was between 6 and 22%.

CONCLUSIONS

According to the analysis of 15-year data, the herniated organs, multiple malformations, as well as the mode of delivery influence the survival in a large number of cases. Early diagnosis predicts a large hernia, a higher malformation rate, and a less favourable prognosis.

Prenatal detection and outcome of congenital diaphragmatic hernia (CDH) associated with deletion of chromosome 15q26: Two patients and review of the literature

Congenital diaphragmatic hernia (CDH) is a severe birth defect characterized by a defect in the diaphragm with pulmonary hypoplasia and postnatal pulmonary hypertension. Approximately 50% of CDH cases are associated with other non-pulmonary congenital anomalies (so called non-isolated CDH) and in 5-10% of cases there is a chromosomal etiology. The majority of CDH cases are detected prenatally. In some cases prenatal chromosome analysis reveals a causative chromosomal anomaly, most often aneuploidy. Deletion of 15q26 is the most frequently described structural chromosomal aberration in patients with non-isolated CDH. In this paper we report on two patients with a deletion of 15q26 and phenotypes similar to other patients with CDH caused by 15q26 deletions. This phenotype consists of intra-uterine growth retardation, left-sided CDH, cardiac anomalies and characteristic facial features, similar to those seen in Fryns syndrome. We propose that when this combination of birth defects is identified, either pre- or postnatally, further investigations to confirm or exclude a deletion of 15q26 are indicated, since the diagnosis of this deletion will have major consequences for the prognosis and, therefore, can affect decision making.

Teratogen-induced, dietary and genetic models of congenital diaphragmatic hernia share a common mechanism of pathogenesis

Congenital diaphragmatic hernia (CDH) is a frequently occurring, major congenital abnormality that has high mortality and significant morbidity in survivors. Currently, the pathogenesis of CDH is poorly understood. In this study, we have compared the anatomical characteristics of diaphragm defects in the well-described nitrofen model with the pathogenesis of CDH in vitamin A-deficient rats and wt1 null-mutant mice, representing teratogen-induced, dietary and genetic models of CDH, respectively. Our histological investigations, aided by three-dimensional reconstruction of the developing diaphragm, revealed a common pathogenic mechanism with regards to the location of the diaphragm defect in the foramen of Bochdalek (posterolateral diaphragm) and specific abnormalities within the primordial diaphragm. Furthermore, our analysis of postmortem specimens highlighted similarities in human cases of CDH and these animal models, supporting our hypothesis that CDH in humans arises from a defect in the primordial diaphragm. Immunohistochemical data were consistent with the defect in the primordial diaphragm being in the nonmuscular component. Importantly, these data show that very distinct models of CDH all share a common pathogenic mechanism and, together with supporting evidence from pathological specimens, highlight our proposed pathogenic model for CDH.

Array comparative genomic hybridization in patients with congenital diaphragmatic hernia: mapping of four CDH-critical regions and sequencing of candidate genes at 15q26.1–15q26.2

Congenital diaphragmatic hernia (CDH) is a common birth defect with a high mortality and morbidity. There have been few studies that have assessed copy number changes in CDH. We present array comparative genomic hybridization data for 29 CDH patients to identify and map chromosome aberrations in this disease. Three patients with 15q26.1-15q26.2 deletions had heterogeneous breakpoints that overlapped with the critical 4 Mb region previously delineated for CDH, confirming 15q26.1-15q26.2 as a critical region for CDH. The three other most compelling CDH-critical regions for genomic deletions based on these data and a literature review are located at chromosomes 8p23.1, 4p16.3-4pter, and 1q41-1q42.1. Based on these recurrent deletions at 15q26.1-15q26.2, we hypothesized that loss-of-function mutations in a gene or genes from this region could cause CDH and sequenced six candidate genes from this region in more than 100 patients with CDH. For three of these genes (CHD2, ARRDC4, and RGMA), we identified missense changes and that were not identified in normal controls; however, none of these alterations appeared unambiguously causal with CDH. These data suggest that CDH caused by chromosome deletions at 15q26.2 may arise because of a contiguous gene deletion syndrome or may have a multifactorial etiology. In addition, there is evidence for substantial genetic heterogeneity in CDH and diaphragmatic hernias can be non-penetrant in patients who have deletions involving CDH-critical regions.

Prenatal diagnosis ofde novo deletions of 8p23.1 or 15q26.1 in two fetuses with diaphragmatic hernia and congenital heart defects

OBJECTIVE

To show the importance of using high-resolution chromosome analysis and FISH-technique for finding subtle chromosomal lesions in prenatal diagnosis specially when there are abnormal ultrasound findings.

METHODS

Ecographic examination of the fetus. GTG banded chromosome and FISH analysis using subtelomeric probes on amniocytes.

RESULTS

We report two prenatal cases with congenital diaphragmatic hernia (CDH) and congenital heart defects (CHDs) with different deletions confirmed by FISH: del(8)(p23.1p23.1) and del(15)(q26.1).

CONCLUSION

These cases support the evidence that the regions 15q26.1 and 8p23.1 may play an important role in the development of the diaphragm. A deletion 8p23.1 or 15q26.1 should be considered whenever a CDH and/or a cardiac abnormality are detected on ultrasound.

Associated malformations in congenital diaphragmatic hernia cases in the last 15 years in a tertiary referral institute

This is a review of cases of perinatally diagnosed congenital diaphragmatic hernia (CDH) with associated malformations with regard to time of diagnosis, side of hernia, associated malformations, and outcome. The authors analyzed the data of CDH cases with associated malformations from records of the I. Department of Obstetrics and Gynecology, Semmelweis University Faculty of Medicine, Budapest, between July 1, 1990 and June 30, 2005. The observed period was analyzed in two parts. The pre- and postnatal examinations verified CDH in 100 cases, 71% of which were associated with other malformations. In 52% (37/71) CDH was diagnosed before the 24th week of gestation. The rate of early diagnosed cases doubled in the second period. Ten percent (7/71) of cases were verified postnatally. Between 1990 and 1997, the percentage of right-sided hernia was 6% (2/34) while in the second period it was 19% (7/37). The association with cardiovascular, chest, and craniofacial anomalies doubled in the second period, while association of central nervous system anomalies halved. Chromosome anomalies were verified in four cases. Pregnancy was terminated in 53% (34/64) and 13% (4/30) of newborn infants survived the perinatal period. Intrauterine or intrapartum death occurred in 8% (5/64) of cases. The prevalence of cardiovascular, pulmonary, and craniofacial anomalies doubled, while that of central nervous system malformations decreased. The prevalence of other associated malformations has not changed significantly between the two periods. The improvement of technical facilities and accumulated experience make it possible to identify a higher number of associated malformations before the 24th week of gestation.

Congenital diaphragmatic hernia: a retinoid-signaling pathway disruption during lung development?

Congenital diaphragmatic hernia (CDH) usually occurs sporadically. The prognosis remains poor, with a 50% perinatal mortality rate. Most deaths result from hypoxemia due to lung hypoplasia and abnormal development of pulmonary vasculature that results in persistent pulmonary hypertension. Our current understanding of the pathogenesis of CDH is based on an assumption linking herniation of abdominal viscera into the thorax with compression of the developing lung. Pulmonary hypoplasia, however, can also result from reduced distension of the developing lung secondary to impaired fetal breathing movements. Moreover, a nitrofen-induced CDH model shows that lung hypoplasia precedes the diaphragmatic defect, leading to a "dual-hit hypothesis." Recent data reveal the role of a retinoid-signaling pathway disruption in the pathogenesis of CDH. We describe the clinical and epidemiological aspects of human CDH, the metabolic and molecular aspects of the retinoid-signaling pathway, and the implications of retinoids in the development of the diaphragm and the lung. Finally, we highlight the existing links between CDH and disruption of the retinoid-signaling pathway, which may suggest an eventual use of retinoids in the treatment of CDH.

Ring chromosome 15: characterization by array CGH

Ring chromosome 15 [r(15)] is an uncommon finding with less than 50 patients reported. Precise genotype-phenotype correlations are problematic because of the difficulties in determining the extent of euchromatic loss, the level of mosaicism, and the influence of the timing of ascertainment. We report two discordant examples of r(15) patients. In the first case, prenatal diagnosis of a de novo r(15) was made during the second trimester: mos 46,XX,r(15)(p11.2q26)[32]/45,XX,-15[13]/47,XX,r(15)(p11.2q26)x2[3]/46,XX,dic r(15)(p11.2q26p11.2q26[1]/46,XX[2]. Postnatal follow-up revealed extremely small stature, heart defects, and developmental delay. Patient 2 was a 31-year-old short-statured female who was living independently: 46,XX,r(15)(p11q26). Both cases showed loss of the 15q subtelomeric region by fluorescence in situ hybridization (FISH). To investigate the discordance in phenotypes between the two patients, we undertook array comparative genomic hybridization (array CGH) analyses to more fully characterize the deletions associated with these otherwise structurally indistinguishable r(15) chromosomes from conventional cytogenetic analyses and fluorescence in situ hybridization (FISH) studies. By array CGH, patient 1 showed deletion of multiple contiguous clones predicting an approximately 6 Mb deletion of distal 15q. In contrast, patient 2 showed loss of just the 15q subtelomeric clone and an interstitial clone by array CGH confirming that the severity of the phenotype correlated with the size of the deletion at the molecular level. These cases illustrate the utility of array CGH characterization for determining the size of the associated deletion in ring chromosomes and for facilitating phenotype-genotype correlations.

Infants with Bochdalek diaphragmatic hernia: sibling precurrence and monozygotic twin discordance in a hospital-based malformation surveillance program

Congenital diaphragmatic hernia (CDH) is a common and often devastating birth defect. In order to learn more about possible genetic causes, we reviewed and classified 203 cases of the Bochdalek hernia type identified through the Brigham and Women's Hospital (BWH) Active Malformation Surveillance Program over a 28-year period. Phenotypically, 55% of the cases had isolated CDH, and 45% had complex CDH defined as CDH in association with additional major malformations or as part of a syndrome. When classified according to likely etiology, 17% had a Recognized Genetic etiology for their CDH, while the remaining 83% had No Apparent Genetic etiology. Detailed analysis using this largest cohort of consecutively collected cases of CDH showed low precurrence among siblings. Additionally, there was no concordance for CDH among five monozygotic twin pairs. These findings, in conjunction with previous reports of de novo dominant mutations in patients with CDH, suggest that new mutations may be an important mechanism responsible for CDH. The twin data also raise the possibility that epigenetic abnormalities contribute to the development of CDH.

Congenital diaphragmatic hernia in a patient with tetrasomy 9p

Tetrasomy of the short arm of chromosome 9 constitutes a rare condition resulting in a well clinically recognized syndrome. In our case, in addition to the characteristic phenotype at birth, the existence of a hernia-type Bochdalek diaphragmatic defect was found. Cytogenetic analysis revealed a nonmosaic case of an isochromosome of the entire short arm of chromosome 9 with no involvement of the heterochromatic region of the long arm: 47, XX, +i (9p). Because chromosome 9 contains several gene locus for enzymes and receptors of the retinoid pathway, this case potentially contributes to retinoid hypothesis in the etiology of congenital diaphragmatic hernia.

Terminal deletion of chromosome 15q26.1: case report and brief literature review

Terminal deletions of chromosome 15q are rare events, with only six cases previously described. Here we describe a seventh case of a terminal deletion of the long arm of chromosome 15, with the present case exhibiting clinical features not previously described.

Congenital diaphragmatic hernia and chromosome 15q26: determination of a candidate region by use of fluorescent in situ hybridization and array-based comparative genomic hybridization

Congenital diaphragmatic hernia (CDH) has an incidence of 1 in 3,000 births and a high mortality rate (33%-58%). Multifactorial inheritance, teratogenic agents, and genetic abnormalities have all been suggested as possible etiologic factors. To define candidate regions for CDH, we analyzed cytogenetic data collected on 200 CDH cases, of which 7% and 5% showed numerical and structural abnormalities, respectively. This study focused on the most frequent structural anomaly found: a deletion on chromosome 15q. We analyzed material from three of our patients and from four previously published patients with CDH and a 15q deletion. By using array-based comparative genomic hybridization and fluorescent in situ hybridization to determine the boundaries of the deletions and by including data from two individuals with terminal 15q deletions but without CDH, we were able to exclude a substantial portion of the telomeric region from the genetic etiology of this disorder. Moreover, one patient with CDH harbored a small interstitial deletion. Together, these findings allowed us to define a minimal deletion region of approximately 5 Mb at chromosome 15q26.1-26.2. The region contains four known genes, of which two--NR2F2 and CHD2--are particularly intriguing gene candidates for CDH.