Trends in congenital anomalies in Europe from 1980 to 2012

BACKGROUND

Surveillance of congenital anomalies is important to identify potential teratogens.

METHODS

This study analysed the prevalence of 61 congenital anomaly subgroups (excluding chromosomal) in 25 population-based EUROCAT registries (1980-2012). Live births, fetal deaths and terminations of pregnancy for fetal anomaly were analysed with multilevel random-effects Poisson regression models.

RESULTS

Seventeen anomaly subgroups had statistically significant trends from 2003-2012; 12 increasing and 5 decreasing.

CONCLUSIONS

The annual increasing prevalence of severe congenital heart defects, single ventricle, atrioventricular septal defects and tetralogy of Fallot of 1.4% (95% CI: 0.7% to 2.0%), 4.6% (1.0% to 8.2%), 3.4% (1.3% to 5.5%) and 4.1% (2.4% to 5.7%) respectively may reflect increases in maternal obesity and diabetes (known risk factors). The increased prevalence of cystic adenomatous malformation of the lung [6.5% (3.5% to 9.4%)] and decreased prevalence of limb reduction defects [-2.8% (-4.2% to -1.5%)] are unexplained. For renal dysplasia and maternal infections, increasing trends may be explained by increased screening, and deceases in patent ductus arteriosus at term and increases in craniosynostosis, by improved follow up period after birth and improved diagnosis. For oesophageal atresia, duodenal atresia/stenosis and ano-rectal atresia/stenosis recent changes in prevalence appeared incidental when compared with larger long term fluctuations. For microcephaly and congenital hydronephrosis trends could not be interpreted due to discrepancies in diagnostic criteria. The trends for club foot and syndactyly disappeared once registries with disparate results were excluded. No decrease in neural tube defects was detected, despite efforts at prevention through folic acid supplementation.

Prenatal diagnosis of urinary tract anomalies, a cohort study in the Northern Netherlands

OBJECTIVE

To describe prevalence, time of diagnosis, and type of birth in children and fetuses with urinary tract (UT) anomalies after the introduction of the anomaly scan in the Netherlands in 2007.

METHODS

We selected, from a population-based congenital anomaly registry, children and fetuses with UT anomalies born between 2008 and 2014. Cases were defined according to type of UT anomaly and whether isolated or with associated anomalies. Information was collected on time of diagnosis and type of birth.

RESULTS

We included 487 cases. Total prevalence increased from 34.0 in 2008 to 42.3 per 10 000 births in 2014, mainly by an increase in anomalies of the collecting system. Almost 70% presented as isolated. Anomalies of the renal parenchyma were more often associated with genetic or other anomalies (47.3%) than anomalies of the collecting system (19.0%). The proportion of prenatally diagnosed cases increased from 59.3% in 2008 to 80.9% in 2014. Termination of pregnancy occurred in 14.8%, of which the majority were UT anomalies associated with a genetic disorder or other anomalies.

CONCLUSION

In the period after the introduction of the anomaly scan, we observed an increasing prevalence of anomalies of the collecting system, but no increase in termination of pregnancies.

Prenatal diagnosis of urinary tract anomalies, a cohort study in the Northern Netherlands

OBJECTIVE

To describe prevalence, time of diagnosis, and type of birth in children and fetuses with urinary tract (UT) anomalies after the introduction of the anomaly scan in the Netherlands in 2007.

METHODS

We selected, from a population-based congenital anomaly registry, children and fetuses with UT anomalies born between 2008 and 2014. Cases were defined according to type of UT anomaly and whether isolated or with associated anomalies. Information was collected on time of diagnosis and type of birth.

RESULTS

We included 487 cases. Total prevalence increased from 34.0 in 2008 to 42.3 per 10 000 births in 2014, mainly by an increase in anomalies of the collecting system. Almost 70% presented as isolated. Anomalies of the renal parenchyma were more often associated with genetic or other anomalies (47.3%) than anomalies of the collecting system (19.0%). The proportion of prenatally diagnosed cases increased from 59.3% in 2008 to 80.9% in 2014. Termination of pregnancy occurred in 14.8%, of which the majority were UT anomalies associated with a genetic disorder or other anomalies.

CONCLUSION

In the period after the introduction of the anomaly scan, we observed an increasing prevalence of anomalies of the collecting system, but no increase in termination of pregnancies.

Maternal occupational exposure and oral clefts in offspring

BACKGROUND

Previous studies suggest that periconceptional maternal occupational exposure to solvents and pesticides increase the risk of oral clefts in the offspring. Less is known about the effect of occupational exposure to metals, dust, and gases and fumes on development of oral clefts.

METHODS

This case-malformed control study used data from a population-based birth defects registry (Eurocat) of children and foetuses born in the Northern Netherlands between 1997 and 2013. Cases were defined as non-syndromic oral clefts. The first control group had chromosomal/monogenic defects, and the second control group was defined as non-chromosomal/non-monogenic malformed controls. Maternal occupational exposure was estimated through linkage of mothers' occupation with a community-based Job Exposure Matrix (JEM). Multivariate logistic regression was used to estimate the effect of occupational exposures. Odds ratios were adjusted (aORs) for relevant confounders.

RESULTS

A total of 387 cases, 1135 chromosomal and 4352 non-chromosomal malformed controls were included in this study. Prevalence of maternal occupational exposures to all agents was 43.9% and 41.0%/37.7% among cases and controls, respectively. Oral clefts had significantly increased ORs of maternal occupational exposure to pesticides (aOR = 1.7, 95% confidence interval [CI] 1.0-3.1) and dust (aOR = 1.3, 95% CI 1.1-1.6) when using non-chromosomal controls. Subgroup analysis for CL(P) stratified by gender showed a significantly increased risk for male infants exposed to 'other solvents' and exposure to mineral dust for female infants.

CONCLUSION

Our study showed that maternal occupational exposure to pesticides and dust are risk factors for oral clefts in the offspring. Larger studies are needed to confirm this finding.

Prenatal exposure to serotonin reuptake inhibitors and congenital heart anomalies: an exploratory pharmacogenetics study

AIM

To explore the role of pharmacogenetics in determining the risk of congenital heart anomalies (CHA) with prenatal use of serotonin reuptake inhibitors.

METHODS

We included 33 case-mother dyads and 2 mother-only (child deceased) cases of CHA in a case-only study. Ten genes important in determining fetal exposure to serotonin reuptake inhibitors were examined: CYP1A2, CYP2C9, CYP2C19, CYP2D6, ABCB1, SLC6A4, HTR1A, HTR1B, HTR2A and HTR3B.

RESULTS

Among the exposed cases, polymorphisms that tended to be associated with an increased risk of CHA were SLC6A4 5-HTTLPR and 5-HTTVNTR, HTR1A rs1364043, HTR1B rs6296 and rs6298 and HTR3B rs1176744, but none reached statistical significance due to our limited sample sizes.

CONCLUSION

We identified several polymorphisms that might potentially affect the risk of CHA among exposed fetuses, which warrants further investigation.

Knowledge and attitude regarding pharmacogenetics among formerly pregnant women in the Netherlands and their interest in pharmacogenetic research

Background

Pharmacogenetics is an emerging field currently being implemented to improve safety when prescribing drugs. While many women who take drugs during pregnancy would likely benefit from such personalized drug therapy, data is lacking on the awareness towards pharmacogenetics among women. We aim to determine the level of knowledge and acceptance of formerly pregnant women in the Netherlands regarding pharmacogenetics and its implementation, and their interest in pharmacogenetic research.

Methods

A population-based survey using postal questionnaires was conducted among formerly pregnant women in the Northern parts of the Netherlands. A total of 986 women were invited to participate.

Results

Of the 219 women who returned completed questionnaires (22.2% response rate), only 22.8% had heard of pharmacogenetics, although the majority understood the concept (64.8%). Women who had experience with drug side-effects were more likely to know about pharmacogenetics [OR = 2.06, 95% CI 1.16, 3.65]. Of the respondents, 53.9% were positive towards implementing pharmacogenetics in their future drug therapy, while 46.6% would be willing to participate in pharmacogenetic research. Among those who were either not willing or undecided in this regard, their concerns were about the consequences of the pharmacogenetic test, including the privacy and anonymity of their genetic information.

Conclusion

The knowledge and attitude regarding the concept of pharmacogenetics among our population of interest is good. Also, their interest in pharmacogenetic research provides opportunities for future research related to drug use during pregnancy and fetal outcome.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-017-1290-z) contains supplementary material, which is available to authorized users.

Maternal use of drug substrates of placental transporters and the effect of transporter-mediated drug interactions on the risk of congenital anomalies

BACKGROUND

A number of transporter proteins are expressed in the placenta, and they facilitate the placental transfer of drugs. The inhibition of P-glycoprotein (P-gp) was previously found to be associated with an increase in the risk of congenital anomalies caused by drug substrates of this transporter. We now explore the role of other placental transporter proteins.

METHODS

A population-based case-referent study was performed using cases with congenital anomalies (N = 5,131) from EUROCAT Northern Netherlands, a registry of congenital anomalies. The referent population (N = 31,055) was selected from the pregnancy IADB.nl, a pharmacy prescription database.

RESULTS

Ten placental transporters known to have comparable expression levels in the placenta to that of P-gp, were selected in this study. In total, 147 drugs were identified to be substrates, inhibitors or inducers, of these transporters. Fifty-eight of these drugs were used by at least one mother in our cases or referent population, and 28 were used in both. The highest user rate was observed for the substrates of multidrug resistance-associated protein 1, mainly folic acid (6% of cases, 8% of referents), and breast cancer resistance protein, mainly nitrofurantoin (2.3% of cases, 2.9% of referents). In contrast to P-gp, drug interactions involving substrates of these transporters did not have a significant effect on the risk of congenital anomalies.

CONCLUSIONS

Some of the drugs which are substrates or inhibitors of placental transporters were commonly used during pregnancy. No significant effect of transporter inhibition was found on fetal drug exposure, possibly due to a limited number of exposures.

Exposure to reactive intermediate-inducing drugs during pregnancy and the incident use of psychotropic medications among children

PURPOSE

Our study aimed to investigate the association between prenatal exposure to reactive intermediate (RI)-inducing drugs and the initiation of psychotropic medications among children.

METHODS

We designed a cohort study using a pharmacy prescription database. Pregnant women were considered exposed when they received a prescription of RI-inducing drugs. These drugs could be either used alone (RI+/FAA-) or combined with drugs exhibiting folic acid antagonism (FAA, RI+/FAA+). The reference group included pregnant women who did not receive any RI-inducing drugs or FAA drugs.

RESULTS

We analyzed 4116 exposed and 30 422 reference pregnancies. The hazard ratio (HR) with 95% confidence interval (CI) was 1.27 (95%CI 1.15-1.41) for pregnancies exposed to RI-inducing drugs as a whole. Considering subgroups of RI-inducing drugs, prenatal exposure to both RI+/FAA+ and RI+/FAA- was associated with the children's initiation of psychotropic medications, HRs being 1.35 (95%CI 1.10-1.66) and 1.26 (1.13-1.41), respectively. The HRs were increased with prolonged exposure to RI-inducing drugs, especially in the first and second trimesters. In a detailed examination of the psychotropics, the incidences of receiving antimigraine preparations and psychostimulants were significantly increased for the exposed children, compared with the reference children. The incidences of receiving antipsychotics and hypnotics were also higher for the exposed children; however, the HRs did not reach significance after adjustment.

CONCLUSIONS

We found a significantly increased incident use of psychotropic medications among children prenatally exposed to RI-inducing drugs, especially during the first and second trimesters. This suggests a detrimental effect during critical periods of brain development. Copyright © 2017 John Wiley & Sons, Ltd.

Prevalence of microcephaly in Europe: population based study

OBJECTIVES

 To provide contemporary estimates of the prevalence of microcephaly in Europe, determine if the diagnosis of microcephaly is consistent across Europe, and evaluate whether changes in prevalence would be detected using the current European surveillance performed by EUROCAT (the European Surveillance of Congenital Anomalies).

DESIGN

 Questionnaire and population based observational study.

SETTING

 24 EUROCAT registries covering 570 000 births annually in 15 countries.

PARTICIPANTS

 Cases of microcephaly not associated with a genetic condition among live births, fetal deaths from 20 weeks' gestation, and terminations of pregnancy for fetal anomaly at any gestation.

MAIN OUTCOME MEASURES

 Prevalence of microcephaly (1 Jan 2003-31 Dec 2012) analysed with random effects Poisson regression models to account for heterogeneity across registries.

RESULTS

 16 registries responded to the questionnaire, of which 44% (7/16) used the EUROCAT definition of microcephaly (a reduction in the size of the brain with a skull circumference more than 3 SD below the mean for sex, age, and ethnic origin), 19% (3/16) used a 2 SD cut off, 31% (5/16) were reliant on the criteria used by individual clinicians, and one changed criteria between 2003 and 2012. Prevalence of microcephaly in Europe was 1.53 (95% confidence interval 1.16 to 1.96) per 10 000 births, with registries varying from 0.4 (0.2 to 0.7) to 4.3 (3.6 to 5.0) per 10 000 (χ(2)=338, df=23, I(2)=93%). Registries with a 3 SD cut off reported a prevalence of 1.74 per 10 000 (0.86 to 2.93) compared with those with the less stringent 2 SD cut off of 1.21 per 10 000 (0.21 to 2.93). The prevalence of microcephaly would need to increase in one year by over 35% in Europe or by over 300% in a single registry to reach statistical significance (P<0.01).

CONCLUSIONS

 EUROCAT could detect increases in the prevalence of microcephaly from the Zika virus of a similar magnitude to those observed in Brazil. Because of the rarity of microcephaly and discrepant diagnostic criteria, however, the smaller increases expected in Europe would probably not be detected. Clear diagnostic criteria for microcephaly must be adopted across Europe.

The Risk of Congenital Heart Anomalies Following Prenatal Exposure to Serotonin Reuptake Inhibitors-Is Pharmacogenetics the Key?

Serotonin reuptake inhibitors (SRIs) are often prescribed during pregnancy. Previous studies that found an increased risk of congenital anomalies, particularly congenital heart anomalies (CHA), with SRI use during pregnancy have created concern among pregnant women and healthcare professionals about the safety of these drugs. However, subsequent studies have reported conflicting results on the association between CHA and SRI use during pregnancy. These discrepancies in the risk estimates can potentially be explained by genetic differences among exposed individuals. In this review, we explore the potential pharmacogenetic predictors involved in the pharmacokinetics and mechanism of action of SRIs, and their relation to the risk of CHA. In general, the risk is dependent on the maternal concentration of SRIs and the foetal serotonin level/effect, which can be modulated by the alteration in the expression and/or function of the metabolic enzymes, transporter proteins and serotonin receptors involved in the serotonin signalling of the foetal heart development. Pharmacogenetics might be the key to understanding why some children exposed to SRIs develop a congenital heart anomaly and others do not.

P-Glycoprotein-Mediated Drug Interactions in Pregnancy and Changes in the Risk of Congenital Anomalies: A Case-Reference Study

Introduction

Drug use in pregnancy is very common but may cause harm to the fetus. The teratogenic effect of a drug is partly dependent on the drug level in the fetal circulation, which is associated with the transport across the placenta. Many drugs are substrates of P-glycoprotein (P-gp), an efflux transporter that acts as a protective barrier for the fetus. We aim to identify whether drug interactions associated with P-gp promote any changes in fetal drug exposure, as measured by the risk of having children with congenital anomalies.

Methods

In this study, cases (N = 4634) were mothers of children with congenital anomalies registered in the EUROCAT Northern Netherlands registry, and the reference population were mothers of children (N = 25,126) from a drug prescription database (IADB.nl).

Results

Drugs that are associated with P-gp transport were commonly used in pregnancy in cases (10 %) and population (12 %). Several drug classes, which are substrates for P-gp, were shown to have a higher user rate in mothers of cases with specific anomalies. The use of this subset of drugs in combination with other P-gp substrates increased the risk for specific anomalies (odds ratio [OR] 4.17, 95 % CI 1.75–9.91), and the addition of inhibitors further increased the risk (OR 13.03, 95 % CI 3.37–50.42). The same pattern of risk increment was observed when the drugs were analyzed separately according to substrate specificity.

Conclusions

The use of drugs associated with P-gp transport was common during pregnancy. For several drug classes associated with specific anomalies, P-gp-mediated drug interactions are associated with an increased risk for those specific anomalies.

Electronic supplementary material

The online version of this article (doi:10.1007/s40264-015-0299-3) contains supplementary material, which is available to authorized users.

When the right (Drug) should be left: Prenatal drug exposure and heterotaxy syndrome

BACKGROUND

Recent studies reported an association between prenatal propylthiouracil exposure and birth defects, including abnormal arrangement across the left-right body axis, suggesting an association with heterotaxy syndrome.

METHODS

This case-control and case-finding study used data from 1981 to 2013 from the EUROCAT birth defect registry in the Northern Netherlands. First, we explored prenatal exposures in heterotaxy syndrome (cases) and Down syndrome (controls). Second, we describe the specific birth defects in offspring of mothers using propylthiouracil (PTU) prenatally.

RESULTS

A total of 66 cases with heterotaxy syndrome (incidence 12.1 per 100,000 pregnancies) and 783 controls with Down syndrome (143.3 per 100,000 pregnancies) were studied. No differences in intoxication use during pregnancy were found between cases and controls, including smoking (28.0% vs. 22.7%; p = 0.40), alcohol (14.0% vs. 26.9%; p = 0.052), and recreational drugs (0 vs. 0.3%; p = 1.00). We found an association between heterotaxy syndrome and prenatal drug exposure to follitropin-alfa (5.6% vs. 1.1%; p = 0.04), and drugs used in nicotine dependence (3.7% vs. 0.2%; p = 0.02). Five mothers used PTU during pregnancy and gave birth to a child with trisomy 18, renal abnormalities, or hypospadias and cardiac defects.

CONCLUSION

This study identified follitropin-alfa and drugs used in nicotine dependence as possible teratogens of heterotaxy syndrome. Our data suggest the possibility that there is an increased risk of birth defects (including renal, urological, and cardiac abnormalities) in children born among mothers taking PTU prenatally, but not for heterotaxy syndrome. Birth Defects Research (Part A) 106:573-579, 2016. © 2016 Wiley Periodicals, Inc.

Folic acid supplementation influences the distribution of neural tube defect subtypes: A registry-based study

Periconceptional folic acid (FA) reduces neural tube defect (NTD) risk, but seems to have a varying effect per NTD subtype. We aimed to study the effect of FA supplementation on NTD subtype distribution using data from EUROCAT Northern Netherlands. We included all birth types with non-syndromal NTDs born in 1997-2012. By Fisher's exact test we analyzed possible differences in NTD subtype distribution between a correct FA supplementation group and incorrect FA supplementation group. We found proportionally fewer cervical/thoracic spina bifida cases and more lumbar/sacral spina bifida cases in the correct FA supplementation group, irrespective of the presence of the main NTD risk factors. The effect on NTD subtype distribution was only seen when FA supplementation was started before conception. We conclude that FA not only prevents the occurrence of a significant proportion of NTDs, but might also decrease the severity of NTDs, as long as supplementation is started before conception.

Pharmacogenetics of drug-induced birth defects: the role of polymorphisms of placental transporter proteins

One of the ongoing issues in perinatal medicine is the risk of birth defects associated with maternal drug use. The teratogenic effect of a drug depends, apart from other factors, on the exposition of the fetus to the drug. Transporter proteins are known to be involved in the pharmacokinetics of drugs and have an effect on drug level and fetal drug exposure. This condition may subsequently alter the risk of teratogenicity, which occurs in a dose-dependent manner. This review focuses on the clinically important polymorphisms of transporter proteins and their effects on the mRNA and protein expression in placental tissue. We also propose a novel approach on how the different genotypes of the polymorphism can be translated into phenotypes to facilitate genetic association studies. The last section looks into the recent studies exploring the association between P-glycoprotein polymorphisms and the risk of fetal birth defects associated with medication use during pregnancy.

Congenital anomalies in offspring of subfertile couples: a registry-based study in the northern Netherlands

OBJECTIVE

To study whether specific congenital anomalies occur more often with a history of subfertility and/or the use of in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI).

DESIGN

Case-only analyses.

SETTING

Not applicable.

PATIENT(S)

We included live births, stillbirths, and terminated pregnancies with congenital anomalies without a known cause that had a birth year between 1997 and 2010 (n = 4,525). A total of 4,185 malformed cases were born to fertile couples and 340 to subfertile couples, of whom 139 had conceived after IVF/ICSI and 201 had conceived naturally after >12 months.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The contribution, expressed in odds ratios (ORs), of a history of subfertility and IVF/ICSI to each specific type of congenital anomaly, imprinting disorder, and syndromal disorder.

RESULT(S)

We found subfertility to be associated with an increase in abdominal wall defects (adjusted OR [aOR] 2.43, 95% CI 1.05-5.62), penoscrotal hypospadia (aOR 9.83, 95% CI 3.58-27.04), right ventricular outflow tract obstruction (aOR 1.77, 95% CI 1.06-2.97), and methylation defects causing imprinting disorders (aOR 13.49, 95% CI 2.93-62.06). In vitro fertilization/ICSI was associated with an increased risk of polydactyly (OR 4.83, 95% CI 1.39-16.77) and more specifically polydactyly of the hands (OR 5.02, 95% CI 1.43-17.65).

CONCLUSION(S)

In our registry-based study, parental subfertility was associated with an increase in abdominal wall defects, penoscrotal hypospadia, right ventricular outflow tract obstruction, and methylation defects causing imprinting disorders. In vitro fertilization/ICSI was associated with an increase in polydactyly, mainly of the hands.

Impact of introduction of 20-week ultrasound scan on prevalence and fetal and neonatal outcomes in cases of selected severe congenital heart defects in The Netherlands

OBJECTIVES

To evaluate in a population-based cohort the effect of the introduction of the 20-week ultrasound scan in 2007 on the time of diagnosis, pregnancy outcome and total prevalence and liveborn prevalence of cases with selected congenital heart defects (CHDs) in The Netherlands.

METHODS

We included children and fetuses diagnosed with selected severe CHD, born in the 11-year period from 2001 to 2011. Two groups of CHD were defined: those associated with an abnormal four-chamber view at ultrasound (Group 1), and those associated with a normal four-chamber view at ultrasound (Group 2). The time of diagnosis, pregnancy outcome and total liveborn prevalence were compared for both groups over two 5-year periods, before and after the introduction of the 20-week ultrasound scan. Trends in total and liveborn prevalence were examined over 2001 to 2011.

RESULTS

Information was collected on 269 children and fetuses. After the introduction of the 20-week ultrasound scan, the prenatal detection rate of CHDs increased in both groups (Group 1, 34.6% in 2001-2005 vs 84.8% in 2007-2011 (P < 0.001); Group 2, 14.3% in 2001-2005 vs 29.6% in 2007-2011 (P = 0.037)). The rate of termination of pregnancy (TOP) increased significantly only for Group 1 (15.4% vs 51.5% (P < 0.001)). The total prevalence of CHD in Group 1 increased over time from 2.9 per 10 000 births in 2001 to 6.4 per 10 000 births in 2011 (P = 0.016). The liveborn prevalence did not show a trend over time. For Group 2, no trends in total or liveborn prevalence could be detected over time.

CONCLUSIONS

Since the implementation of the routine 20-week ultrasound scan in The Netherlands, prenatal detection rate of selected severe CHDs increased significantly. Improved prenatal detection was accompanied by a more than three-fold increase in TOP, although only in those CHDs with an abnormal four-chamber view at prenatal ultrasound.

Screening of TGFBR1, TGFBR2, and FLNA in familial mitral valve prolapse

So far only mutations in the filamin A gene (FLNA) have been identified as causing familial mitral valve prolapse (MVP). Previous studies have linked dysregulation of the transforming growth factor beta (TGF-β) cytokine family to MVP. We investigated whether mutations in the TGF-β receptors genes type I (TGFBR1) and II (TGFBR2) underlie isolated familial MVP cases. Eight families with isolated familial MVP were evaluated clinically and genetically. Ventricular arrhythmias were present in five of the eight families and sudden cardiac death occurred in six patients. Tissue obtained during mitral valve surgery or autopsy was available for histological examination in six cases; all demonstrated myxomatous degeneration. A previously described FLNA missense mutation (p.G288R) was identified in one large family, but no mutations were discovered in TGFBR1 or TGFBR2. An FLNA missense mutation was identified in one family but we found no TGFBR1 or TGFBR2 mutations. Our results suggest that TGFBR1 and TGFBR2 mutations do not play a major role in isolated myxomatous valve dystrophy. Screening for FLNA mutations is recommended in familial myxomatous valvular dystrophy, particularly if X-linked inheritance is suspected.

A novel classification system to predict the pathogenic effects of CHD7 missense variants in CHARGE syndrome

CHARGE syndrome is characterized by the variable occurrence of multisensory impairment, congenital anomalies, and developmental delay, and is caused by heterozygous mutations in the CHD7 gene. Correct interpretation of CHD7 variants is essential for genetic counseling. This is particularly difficult for missense variants because most variants in the CHD7 gene are private and a functional assay is not yet available. We have therefore developed a novel classification system to predict the pathogenic effects of CHD7 missense variants that can be used in a diagnostic setting. Our classification system combines the results from two computational algorithms (PolyPhen-2 and Align-GVGD) and the prediction of a newly developed structural model of the chromo- and helicase domains of CHD7 with segregation and phenotypic data. The combination of different variables will lead to a more confident prediction of pathogenicity than was previously possible. We have used our system to classify 145 CHD7 missense variants. Our data show that pathogenic missense mutations are mainly present in the middle of the CHD7 gene, whereas benign variants are mainly clustered in the 5' and 3' regions. Finally, we show that CHD7 missense mutations are, in general, associated with a milder phenotype than truncating mutations.

The results of CHD7 analysis in clinically well-characterized patients with Kallmann syndrome

CONTEXT

Kallmann syndrome (KS) and CHARGE syndrome are rare heritable disorders in which anosmia and hypogonadotropic hypogonadism co-occur. KS is genetically heterogeneous, and there are at least eight genes involved in its pathogenesis, whereas CHARGE syndrome is caused by autosomal dominant mutations in only one gene, the CHD7 gene. Two independent studies showed that CHD7 mutations can also be found in a minority of KS patients.

OBJECTIVE

We aimed to investigate whether CHD7 mutations can give rise to isolated KS or whether additional features of CHARGE syndrome always occur.

DESIGN

We performed CHD7 analysis in a cohort of 36 clinically well-characterized Dutch patients with KS but without mutations in KAL1 and with known status for the KS genes with incomplete penetrance, FGFR1, PROK2, PROKR2, and FGF8.

RESULTS

We identified three heterozygous CHD7 mutations. The CHD7-positive patients were carefully reexamined and were all found to have additional features of CHARGE syndrome.

CONCLUSION

The yield of CHD7 analysis in patients with isolated KS seems very low but increases when additional CHARGE features are present. Therefore, we recommend performing CHD7 analysis in KS patients who have at least two additional CHARGE features or semicircular canal anomalies. Identifying a CHD7 mutation has important clinical implications for the surveillance and genetic counseling of patients.

CHD7 mutations and CHARGE syndrome: the clinical implications of an expanding phenotype

BACKGROUND

CHARGE syndrome is a highly variable, multiple congenital anomaly syndrome, of which the complete phenotypic spectrum was only revealed after identification of the causative gene in 2004. CHARGE is an acronym for ocular coloboma, congenital heart defects, choanal atresia, retardation of growth and development, genital hypoplasia, and ear anomalies associated with deafness. This typical combination of clinical features is caused by autosomal dominant mutations in the CHD7 gene.

OBJECTIVE

To explore the emerging phenotypic spectrum of CHD7 mutations, with a special focus on the mild end of the spectrum.

METHODS

We evaluated the clinical characteristics in our own cohort of 280 CHD7 positive patients and in previously reported patients with CHD7 mutations and compared these with previously reported patients with CHARGE syndrome but an unknown CHD7 status. We then further explored the mild end of the phenotypic spectrum of CHD7 mutations.

RESULTS

We discuss that CHARGE syndrome is primarily a clinical diagnosis. In addition, we propose guidelines for CHD7 analysis and indicate when evaluation of the semicircular canals is helpful in the diagnostic process. Finally, we give updated recommendations for clinical surveillance of patients with a CHD7 mutation, based on our exploration of the phenotypic spectrum and on our experience in a multidisciplinary outpatient clinic for CHARGE syndrome.

CONCLUSION

CHARGE syndrome is an extremely variable clinical syndrome. CHD7 analysis can be helpful in the diagnostic process, but the phenotype cannot be predicted from the genotype.

Anosmia predicts hypogonadotropic hypogonadism in CHARGE syndrome

OBJECTIVE

To test the hypothesis that a smell test could predict the occurrence of hypogonadotropic hypogonadism (HH) in patients with CHARGE syndrome, which is a variable combination of ocular coloboma, heart defects, choanal atresia, retardation of growth/development, genital hypoplasia, and ear anomalies or hearing loss caused by mutations in the CHD7 (chromodomain helicase DNA binding protein 7) gene.

STUDY DESIGN

We performed endocrine studies and smell testing (University of Pennsylvania Smell Identification Test) in 35 adolescent patients with molecularly confirmed CHARGE syndrome.

RESULTS

Complete data on smell and puberty were available for 15 patients; 11 patients had both anosmia and HH, whereas 4 patients had normosmia/hyposmia and spontaneous puberty. In addition, 7 boys were highly suspected of having HH (they were too young for definite HH diagnosis, but all had cryptorchidism, micropenis, or both) and had anosmia. The type of CHD7 mutation could not predict HH because a father and daughter with the same CHD7 mutation were discordant for HH and anosmia.

CONCLUSION

Anosmia and HH were highly correlated in our cohort, and therefore smell testing seems to be an attractive method for predicting the occurrence of HH in patients with CHARGE syndrome. The use of this test could prevent delay of hormonal pubertal induction, resulting in an age-appropriate puberty.

A novel cerebello-ocular syndrome with abnormal glycosylation due to abnormalities in dolichol metabolism

Cerebellar hypoplasia and slowly progressive ophthalmological symptoms are common features in patients with congenital disorders of glycosylation type I. In a group of patients with congenital disorders of glycosylation type I with unknown aetiology, we have previously described a distinct phenotype with severe, early visual impairment and variable eye malformations, including optic nerve hypoplasia, retinal coloboma, congenital cataract and glaucoma. Some of the symptoms overlapped with the phenotype in other congenital disorders of glycosylation type I subtypes, such as vermis hypoplasia, anaemia, ichtyosiform dermatitis, liver dysfunction and coagulation abnormalities. We recently identified pathogenic mutations in the SRD5A3 gene, encoding steroid 5α-reductase type 3, in a group of patients who presented with this particular phenotype and a common metabolic pattern. Here, we report on the clinical, genetic and metabolic features of 12 patients from nine families with cerebellar ataxia and congenital eye malformations diagnosed with SRD5A3-congenital disorders of glycosylation due to steroid 5α-reductase type 3 defect. This enzyme is necessary for the reduction of polyprenol to dolichol, the lipid anchor for N-glycosylation in the endoplasmic reticulum. Dolichol synthesis is an essential metabolic step in protein glycosylation. The current defect leads to a severely abnormal glycosylation state already in the early phase of the N-glycan biosynthesis pathway in the endoplasmic reticulum. We detected high expression of SRD5A3 in foetal brain tissue, especially in the cerebellum, consistent with the finding of the congenital cerebellar malformations. Based on the overlapping clinical, biochemical and genetic data in this large group of patients with congenital disorders of glycosylation, we define a novel syndrome of cerebellar ataxia associated with congenital eye malformations due to a defect in dolichol metabolism.

Death in CHARGE syndrome after the neonatal period

CHARGE syndrome is a multiple congenital anomaly syndrome that can be life-threatening in the neonatal period. Complex heart defects, bilateral choanal atresia, esophageal atresia, severe T-cell deficiency, and brain anomalies can cause neonatal death. As little is known about the causes of death in childhood and adolescence, we studied post-neonatal death in patients with CHARGE syndrome. We collected medical data on three deceased children from a follow-up cohort of 48 CHARGE patients and retrospectively on an additional four deceased patients (age at death 11 months to 22 years). We analyzed the factors that had contributed to their death. In five patients respiratory aspiration had most likely contributed to premature death, one died of post-operative complications, and another choked during eating. From our findings and a literature review, we suggest that swallowing problems, gastro-esophageal reflux disease, respiratory aspiration and post-operative airway events are important contributors to post-neonatal death in CHARGE syndrome. Cranial nerve dysfunction is proposed as the underlying pathogenic mechanism. We recommend every CHARGE patient with feeding difficulties to be assessed by a multidisciplinary team to evaluate cranial nerve function and swallowing. Timely treatment of swallowing problems and gastro-esophageal reflux disease is important. Surgical procedures on these patients should be combined whenever possible because of their increased risk of post-operative complications and intubation problems. Finally, we recommend performing autopsy in deceased CHARGE patients in order to gain more insight into causes of death.

CHD8 interacts with CHD7, a protein which is mutated in CHARGE syndrome

CHARGE syndrome is an autosomal dominant disorder caused in about two-third of cases by mutations in the CHD7 gene. For other genetic diseases e.g. hereditary spastic paraplegia, it was shown that interacting partners are involved in the underlying cause of the disease. These data encouraged us to search for CHD7 binding partners by a yeast two-hybrid library screen and CHD8 was identified as an interacting partner. The result was confirmed by a direct yeast two-hybrid analysis, co-immunoprecipitation studies and by a bimolecular fluorescence complementation assay. To investigate the function of CHD7 missense mutations in the CHD7-CHD8 interacting area on the binding capacity of both proteins, we included three known missense mutations (p.His2096Arg, p.Val2102Ile and p.Gly2108Arg) and one newly identified missense mutation (p.Trp2091Arg) in the CHD7 gene and performed both direct yeast two-hybrid and co-immunoprecipitation studies. In the direct yeast two-hybrid system, the CHD7-CHD8 interaction was disrupted by the missense mutations p.Trp2091Arg, p.His2096Arg and p.Gly2108Arg, whereas in the co-immunoprecipitation studies disruption of the CHD7-CHD8 interaction by the mutations could not be observed. The results lead to the hypothesis that CHD7 and CHD8 proteins are interacting directly and indirectly via additional linker proteins. Disruption of the direct CHD7-CHD8 interaction might change the conformation of a putative large CHD7-CHD8 complex and could be a disease mechanism in CHARGE syndrome.