Inheritance of familial congenital isolated anorectal malformations: case report and review

Associations of anorectal malformations and related syndromes

Anorectal malformations (ARMs) represent a complex group of congenital anomalies resulting from abnormal development of the hindgut, allantois and Mullerian duct resulting in complete or partial urorectal septal malformations. There is a wide variety of phenotypic expression, ranging from mild anorectal to very complex severe ARM with >75 % having other associated malformations. 50 % of cases are syndromic although many may have other associated anomalies. This suggests a genetic link but the genetics of ARM are highly complex with a number of candidate genes being identified. Many can be classified as "field defects" as a result of a complex set of genetic interactions. Patients with associated malformations can be classified into those with multiple congenital anomalies (non-syndromic), those with chromosomal abnormalities and those with non-chromosomal syndromic associations, also, those with non-chromosomal syndromes and the influence of environmental factors (e.g. drugs in pregnancy). Although much is not known about the aetiology of ARM, the weight of evidence points to genetic factors as major causes for the condition. In this review, we look at the chromosomal and genetic associations and their underlying signalling pathways, to obtain a better understanding of the pathogenetic mechanisms involved in developing ARM. The spectrum of ARM phenotypic expression probably results from involvement and crosstalk between a number of critical signalling systems involved in development of this region. As a result, it may be expressed as a "field developmental defect" with many associated abnormalities. The role of environmental factors in the development of ARM is probably less.

Anorectal atresia and variants at predicted regulatory sites in candidate genes

Anorectal atresia is a serious birth defect of largely unknown etiology but candidate genes have been identified in animal studies and human syndromes. Because alterations in the activity of these genes might lead to anorectal atresia, we selected 71 common variants predicted to be in transcription factor binding sites, CpG windows, splice sites, and miRNA target sites of 25 candidate genes, and tested for their association with anorectal atresia. The study population comprised 150 anorectal atresia cases and 623 control infants without major malformations. Variants predicted to affect transcription factor binding, splicing, and DNA methylation in WNT3A, PCSK5, TCF4, MKKS, GLI2, HOXD12, and BMP4 were associated with anorectal atresia based on a nominal P value < 0.05. The GLI2 and BMP4 variants are reported to be moderately associated with gene expression changes (Spearman's rank correlation coefficients between -0.260 and 0.226). We did not find evidence for interaction between maternal pre-pregnancy obesity and variants in MKKS, a gene previously associated with obesity, on the risk of anorectal atresia. Our results for MKKS support previously suggested associations with anorectal malformations. Our findings suggest that more research is needed to determine whether altered GLI2 and BMP4 expression is important in anorectal atresia in humans.

Autosomal-dominant non-syndromic anal atresia: sequencing of candidate genes, array-based molecular karyotyping, and review of the literature

INTRODUCTION

Anorectal malformations (ARM) range from mild anal to severe anorectal anomalies. Approximately 50% are estimated to be non-syndromic with multiple familial cases reported that suggest underlying genetic factors. These, however, still await identification.

MATERIALS AND METHODS

We report a familial case of non-syndromic ARM with a mother and her two children being affected. Mother and daughter had mild ARM that had only been diagnosed after the index patient was born with a more severe form and ultrashort Hirschsprung's disease. To reveal the genetic cause in our family genome-wide array analysis was carried out to ascertain microaberrations characterized by loss or gain of genomic material. In addition, sequence analysis of four major Hirschsprung's disease genes (RET, EDNRB, EDN3, and GDNF) and the HLXB9 gene was performed to identify a mutation common to all three family members; however, these analyses did not reveal any causal genetic alteration. To demonstrate the frequency of familial non-syndromic cases, we performed a literature search revealing 59 families with at least two affected members. Sufficient description of ARM phenotype and affection status of relatives to surely classify them as familial non-syndromic forms was given for 22 families.

CONCLUSION

The present family suggests that mild ARM may be overlooked in patients with non-specific clinical symptoms and that the incidence of ARM may thus be higher than previously estimated. With the new possibilities of whole exome sequencing, even small families hold the possibility to identify causal defects.

Research perspectives in the etiology of congenital anorectal malformations using data of the International Consortium on Anorectal Malformations: evidence for risk factors across different populations

PURPOSE

The recently established International Consortium on Anorectal Malformations aims to identify genetic and environmental risk factors in the etiology of syndromic and nonsyndromic anorectal malformations (ARM) by promoting collaboration through data sharing and combined research activities.

METHODS

The consortium attempts to recruit at least 1,000 ARM cases. DNA samples are collected from case-parent triads to identify genetic factors involved in ARM. Several genetic techniques will be applied, including SNP arrays, gene and whole exome sequencing, and a genome-wide association study. Questionnaires inquiring about circumstances before and during pregnancy will be used to obtain environmental risk factor data.

RESULTS

Currently, 701 ARM cases have been recruited throughout Europe. Clinical data are available from all cases, and DNA samples and questionnaire data mainly from the Dutch and German cases. Preliminary analyses on environmental risk factors in the Dutch and German cohort found associations between ARM and family history of ARM, fever during first trimester of pregnancy and maternal job exposure to cleaning agents and solvents.

CONCLUSION

First results show that both genetic and environmental factors may contribute to the multifactorial etiology of ARM. The International Consortium on Anorectal Malformations will provide possibilities to study and detect important genes and environmental risk factors for ARM, ultimately resulting in better genetic counseling, improved therapies, and primary prevention.

Maternal and paternal risk factors for anorectal malformations: a Dutch case-control study

BACKGROUND

Anorectal malformations (ARM) are major congenital malformations that usually require a multitude of surgical procedures at a very early age and have a large impact on the lives of patients and their parents. The causes of ARM are still largely unknown, but they are assumed to have a multifactorial etiology. A few studies focused on environmental risk factors, but evidence is still scarce.

METHODS

In this Dutch case-control study (1996-2008), we investigated the role of maternal and paternal risk factors in the etiology of ARM. Parents of 85 ARM cases and 650 controls filled in a questionnaire. Controls were children treated with ear ventilation tubes.

RESULTS

A higher occurrence of fever during the first trimester of pregnancy was found for case mothers compared to control mothers (odds ratio [OR], 5.1; 95% Confidence Interval [CI], 0.9, 28.1). Maternal occupational exposure to industrial cleaning agents and solvents increased the risk of ARM three times (OR, 2.9; 95% CI, 0.9, 9.3). Overweight (Body Mass Index [BMI] > or = 25 kg/m(2)) before pregnancy also seemed to be associated with ARM (OR, 1.8; 95% CI, 1.1, 2.8), as well as maternal multivitamin use during pregnancy (OR, 1.6; 95% CI, 1.0, 2.7), paternal smoking (OR, 1.8; 95% CI, 1.1, 2.9), and paternal occupational exposure to exhaust fumes (OR, 1.9; 95% CI, 1.0, 3.6). Reported ARM in at least one first- or second-degree family member greatly increased the risk of having a child with an ARM (OR, 40.3; 95% CI, 4.8, 342.8).

CONCLUSIONS

This study revealed potential risk factors for ARM, including fever during pregnancy, maternal overweight, use of multivitamins, paternal smoking, and occupational exposures, but a familial component seems important as well.

Genetics of Hirschsprung disease and anorectal malformations

Hirschsprung disease (HD) and anorectal malformations (ARMs) result from alterations in hindgut development. It has long been recognized that both recur in families and thus result, at least in part, from genetic factors. Progress in the understanding of the genetic basis of HD has been made by the application of findings from genetic animal models of altered enteric nervous system development to human beings. Several genes have been shown to be important for human enteric nervous system development, and current work is progressing to identify genetic interactions that may explain the variable phenotype of HD. By contrast, understanding of the genetic factors underlying ARMs is much less developed. We and others have shown that genetic factors play an important role in the pathogenesis of ARMs, and many mouse genetic models suggest molecular pathways that may be altered in ARMs.

Anorectal malformation and Down's syndrome in monozygotic twins

Anorectal malformation (ARM) can be divided in high, intermediate, and low forms according to the level of termination of the rectum in relation to the pubococcygeal and ischiatic lines. Patients with Down's syndrome have a high incidence of gastrointestinal anomalies, such as tracheoesophageal fistula, duodenal obstruction, annular pancreas, Hirschsprung's disease, and ARM. In these children, ARM is generally low with or without a fistula. The mode of inheritance of ARM and its genetic relation with Down's syndrome is not known, even if the association (ARM-Down's syndrome) seems not to be coincidental. We describe here a very rare case of monozygotic twins born with the association of ARM and Down's syndrome.

Stability of prevalence rates of anorectal malformations in the Alberta Congenital Anomalies Surveillance System 1990-2004

BACKGROUND/PURPOSE

Anorectal malformations appeared to be increasing in the province of Alberta, Canada. To assess whether this was a significant trend, with the possibility of these having a teratogenic origin, we examined the frequency of anorectal malformations over a 15-year period.

METHODS

We examined the records of the Alberta Congenital Anomaly Surveillance System, which is a semiactive surveillance system using the British Paediatric Association and the Royal College of Paediatrics and Child Health expansions of the International Classification of Diseases-Ninth Revision and the International Classification of Diseases-10th Revision.

RESULTS

The overall rate was 1/2162 (4.63/10,000 total births) with a marked male predominance (1.7:1). Approximately two thirds of the 273 cases had 1 or more malformations.

CONCLUSION

Although there was an increasing trend in the rate from 1999 especially for the multiples, this was not significant. In view of the advances in syndrome identification and molecular diagnostics, consideration should be given to a detailed review of the family history and appropriate testing not only for multiple cases but also for isolated ones.

Isolated imperforate anus in monozygotic twins: case report and implications

The authors report a case of isolated imperforate anus with perineal fistula in monozygotic twins. Only 4 other well-documented cases of monozygotic twins concordant for isolated anorectal malformation have been reported in the literature. In all these cases the defect occurred below the levator ani muscle. This case confirms previous reports on the incidence of low anorectal anomalies in monozygotic twins where the defect was isolated. A review of the literature relating to this condition in twins and siblings points toward low anomalies and more severe malformations having different genetic backgrounds.

Feingold syndrome: clinical review and genetic mapping

Feingold syndrome is characterized by autosomal dominant inheritance of microcephaly and limb malformations, notably hypoplastic thumbs, and clinodactyly of second and fifth fingers. Syndactyly frequently involves the second and third, as well as the fourth and fifth toes. Approximately one in three Feingold syndrome patients have esophageal or duodenal atresia or both. Anal atresia has been reported in a single case. At least 79 patients in 25 families have been reported. The syndrome has autosomal dominant inheritance with full penetrance, and variable expressivity. Vertebral anomalies, cardiac malformations, and deafness have been noted in a minority of patients. Here, we report a patient with hydronephrosis of one kidney and cystic dysplasia of the other, necessitating nephrectomy. The overall pattern of malformations in Feingold syndrome shows considerable overlap with the VATER/VACTERL association. The gene for Feingold syndrome maps to 2p23-p24, but remains to be identified. Comparison of the pattern of anomalies that occurs in the Feingold syndrome in humans and malformations that are present in mice with mutations of genes in the sonic hedgehog signaling pathway suggest, that the elusive Feingold syndrome gene may involve this signaling pathway as well.

An autosomal recessive syndrome of nasal anomalies associated with renal and anorectal malformations

We report a consanguineous Arab family with four children affected with bifid nose associated with renal agenesis and variable degree of anorectal malformations. We suggest that the combination of abnormalities in these children represent a previously undescribed autosomal recessive syndrome.