A review of genetic mutation in familial Hirschsprung's disease in South Africa: towards genetic counseling

Comprehensive characterization of the genetic landscape of familial Hirschsprung's disease

BACKGROUND

Hirschsprung's disease (HSCR) is one of the most common congenital digestive tract malformations and can cause stubborn constipation or gastrointestinal obstruction after birth, causing great physical and mental pain to patients and their families. Studies have shown that more than 20 genes are involved in HSCR, and most cases of HSCR are sporadic. However, the overall rate of familial recurrence in 4331 cases of HSCR is about 7.6%. Furthermore, familial HSCR patients show incomplete dominance. We still do not know the penetrance and genetic characteristics of these known risk genes due to the rarity of HSCR families.

METHODS

To find published references, we used the title/abstract terms "Hirschsprung" and "familial" in the PubMed database and the MeSH terms "Hirschsprung" and "familial" in Web of Science. Finally, we summarized 129 HSCR families over the last 40 years.

RESULTS

The male-to-female ratio and the percentage of short segment-HSCR in familial HSCR are much lower than in sporadic HSCR. The primary gene factors in the syndromic families are ret proto-oncogene (RET) and endothelin B receptor gene (EDNRB). Most families show incomplete dominance and are relevant to RET, and the RET mutation has 56% penetrance in familial HSCR. When one of the parents is a RET mutation carrier in an HSCR family, the offspring's recurrence risk is 28%, and the incidence of the offspring does not depend on whether the parent suffers from HSCR.

CONCLUSION

Our findings will help HSCR patients obtain better genetic counseling, calculate the risk of recurrence, and provide new insights for future pedigree studies.

What parents need to know about Hirschsprung disease

Hirschsprung's disease (HD) is a complex colorectal disorder that can be challenging to understand and overwhelming to many parents. Counseling parents is critical for ensuring they understand their child's condition, how it must be treated, pitfalls that can occur during treatment, and how they will do in the long term. This article breaks down this process into a series of informally worded questions and reviews evidence-based discussion points around the most common concerns parents will have: survival, pathophysiology, surgical correction and complications, etiology and genetic basis, associated issues, outcomes, and familial nature. Where evidence is unclear, expert opinion is included. Discussion is geared towards the parents of a newly diagnosed and otherwise healthy neonate, with a brief section on complex situations including associated syndromes and late diagnosis. Embarking on the longitudinal care of a child with HD is a complex undertaking and requires significant parental education to establish a proper parent-surgeon relationship, an essential factor for optimizing outcome and family satisfaction.

Familial Experience With Hirschsprung's Disease Improves the Patient's Ability to Cope

INTRODUCTION

Familial occurrence of Hirschsprung's disease may have a positive effect on patients' ability to cope with the disease. The aim was to compare long-term bowel function and generic quality of life between patients with familial and non-familial Hirschsprung's disease.

METHODS

This was a nationwide, cross-sectional study in which we included all 830 Hirschsprung patients of 8 years and older who had undergone surgery between 1957 and 2015. We excluded patients with a permanent stoma, intellectual disability, or an unknown or foreign address. We requested patients to complete the validated pediatric or adult Defecation and Fecal Continence questionnaire and the Child Health Questionnaire Child Form-87, or the World Health Organization Quality of Life-100 Assessment Instrument.

RESULTS

We analyzed 336 Hirschsprung patients, 15.8% of whom were familial cases and 84.2% were non-familial cases. After adjusting for aganglionic length, sex, and age, patients with familial Hirschsprung's disease were twice more likely to suffer from constipation (OR = 2.47, 95% CI, 1.21-5.05, p = 0.013). The quality of life of the pediatric patients was comparable, but in adult patients the energy/fatigue, thinking/learning/concentration, and work capacity facets showed better scores in the familial patients with Hirschsprung's disease of the rectosigmoid (p = 0.029, p = 0.024, p = 0.036, respectively).

CONCLUSIONS

Different facets of generic quality of life are better in adult patients with familial Hirschsprung's disease of the rectosigmoid. It seems that familial experience with the disease influences patients' coping abilities positively.

Size matters: Large copy number losses in Hirschsprung disease patients reveal genes involved in enteric nervous system development

Hirschsprung disease (HSCR) is a complex genetic disease characterized by absence of ganglia in the intestine. HSCR etiology can be explained by a unique combination of genetic alterations: rare coding variants, predisposing haplotypes and Copy Number Variation (CNV). Approximately 18% of patients have additional anatomical malformations or neurological symptoms (HSCR-AAM). Pinpointing the responsible culprits within a CNV is challenging as often many genes are affected. Therefore, we selected candidate genes based on gene enrichment strategies using mouse enteric nervous system transcriptomes and constraint metrics. Next, we used a zebrafish model to investigate whether loss of these genes affects enteric neuron development in vivo.

This study included three groups of patients, two groups without coding variants in disease associated genes: HSCR-AAM and HSCR patients without associated anomalies (HSCR-isolated). The third group consisted of all HSCR patients in which a confirmed pathogenic rare coding variant was identified. We compared these patient groups to unaffected controls. Predisposing haplotypes were determined, confirming that every HSCR subgroup had increased contributions of predisposing haplotypes, but their contribution was highest in isolated HSCR patients without RET coding variants. CNV profiling proved that specifically HSCR-AAM patients had larger Copy Number (CN) losses. Gene enrichment strategies using mouse enteric nervous system transcriptomes and constraint metrics were used to determine plausible candidate genes located within CN losses. Validation in zebrafish using CRISPR/Cas9 targeting confirmed the contribution of UFD1L, TBX2, SLC8A1, and MAPK8 to ENS development. In addition, we revealed epistasis between reduced Ret and Gnl1 expression and between reduced Ret and Tubb5 expression in vivo. Rare large CN losses—often de novo—contribute to HSCR in HSCR-AAM patients. We proved the involvement of six genes in enteric nervous system development and Hirschsprung disease.

Hirschsprung disease is a congenital disorder characterized by the absence of intestinal neurons in the distal part of the intestine. It is a complex genetic disorder in which multiple variations in our genome combined, result in disease. One of these variations are Copy Number Variations (CNVs): large segments of our genome that are duplicated or deleted. Patients often have Hirschsprung disease without other symptoms. However, a proportion of patients has additional associated anatomical malformations and neurological symptoms. We found that CNVs, present in patients with associated anomalies, are more often larger compared to unaffected controls or Hirschsprung patients without other symptoms. Furthermore, Copy Number (CN) losses are enriched for constrained coding regions (CCR; genes usually not impacted by genomic alterations in unaffected controls) of which the expression is higher in the developing intestinal neurons compared to the intestine. We modelled loss of these candidate genes in zebrafish by disrupting the zebrafish orthologues by genome editing. For several genes this resulted in changes in intestinal neuron development, reminiscent of HSCR observed in patients. The results presented here highlight the importance of Copy Number profiling, zebrafish validation and evaluating all CCR expressed in developing intestinal neurons during diagnostic evaluation.

Novel Causative RET Mutation in a Japanese Family with Hirschsprung's Disease: Case Report and Factors Impacting Disease Severity

RET gene variances confer susceptibility to Hirschsprung's disease (HSCR) with pathogenetic mutations being identified in half of familial cases. This investigation of familial HSCR was aimed to clarify the relationship between genetic mutations and clinical phenotype using next-generation sequencing. A novel c2313C > G(D771E) RET mutation was identified in all three affected family members. The mutation involved the kinase domain, which is believe to impair RET activity and intestinal function. A second RET mutation, c1465G > A(D489N), was found only in the extensive aganglionosis case. We conclude that the novel c2313C > A(D771E) mutation in RET may be pathogenic for HSCR, while the c1465C > G(D489N) mutation may be related to phenotype severity.

Outcomes in patients with Hirschsprung disease following definitive surgery

Objective

Several pull-through procedures have been described for Hirschsprung disease (HSCR) with varying outcomes. We aimed to describe the outcomes in HSCR patients < 18 year of age who underwent surgical procedures at Dr. Sardjito Hospital, Yogyakarta, Indonesia from January 2013 to December 2014.

Results

We utilized 67 HSCR patients, of whom 49 (73%) were males and 18 (27%) females. Neonatal presentation was seen in 57 cases (85%) and most patients (98.5%) had short-segment HSCR. The clinical manifestations were mainly abdominal distension (94%) and delayed passage of meconium (45%). The most common definitive treatment performed was transanal endorectal pull-through (TEPT) (54%), followed by Soave (18%) and Duhamel (13%) procedures. Enterocolitis occurred in 13% of the HSCR patients after endorectal pull-through, but did not reach a significant level (p-value = 0.65), while the constipation rate was significantly higher in HSCR patients who underwent posterior neurectomy compared with those other procedures (OR = 15.5, 95% CI = 1.8–132.5; p-value = 0.019). In conclusions, most HSCR patients in Indonesia were diagnosed in the neonatal period and underwent the TEPT procedure. Furthermore, the risk of constipation is increased in HSCR patients following posterior neurectomy compared with other definitive surgical techniques.

Familial Near-Total Intestinal Aganglionosis

Near total aganglionosis represents the most extreme and rare form of Hirschsprung's disease. It can affect more than one member of family. We report three cases of near total intestinal aganglionosis in a family presenting with intestinal obstruction at birth. All of them were operated and a jejunostomy was performed. Outcome was dismal.

Epidemiology of Hirschsprung's Disease in Taiwanese Children: A 13-year Nationwide Population-based Study

BACKGROUND

Hirschsprung's disease (HD) is an important colon disease in children. The aim of this study is to describe the epidemiological features of HD in Taiwanese children.

METHODS

We conducted a study from the Taiwan National Health Insurance Research Database and analyzed cases who received surgical intervention between 1998 and 2010 due to HD (International Classification of Diseases, 9(th) Revision, Clinical Modification 751.3) or megacolon (International Classification of Diseases, 9(th) Revision, Clinical Modification 564.7). The incidence, sex ratio, age at the surgical intervention, associated complication, and medical expenditures were analyzed.

RESULTS

There were a total of 629 HD cases, including 458 boys and 171 girls, with an overall incidence of 2.2 per 10,000 live births. The male-to-female incidence ratio was 2.38. There was no secular trend of incidence across the years. Seventy-two percent of cases received surgical treatment before the age of 1 year. The younger cases had higher operation-related medical expenditures. Those patients with preoperative enterocolitis (EC) had a higher possibility of postoperative EC than those patients without preoperative EC (34.6% vs. 24.3%, p = 0.013). There were 169 (26.9%) HD cases with additional anomalies, the most common being gastrointestinal and circulatory system anomalies. Of these, 12 (1.9%) cases were Down syndrome.

CONCLUSION

The incidence of HD in Taiwanese children, a majority Chinese population, was one per 4545 live births with a male predominance. Preoperative EC was a significant factor that was associated with postoperative EC. The percentage associated with Down syndrome was relatively low, probably due to a prenatal screening program.

Clinical and genetic correlations of familial Hirschsprung's disease

BACKGROUND

The risk of familial transmission in Hirschsprung's disease (HSCR) currently lacks correlation between the clinical phenotype and the underlying genetic factors. The aim of this study was to clinically evaluate familial HSCR transmission and to correlate with the genetic background.

METHODS

Clinical and gene analysis of familial HSCR patients were explored. DNA from 45 patients (35 kindreds) was screened for genetic variations of the RET, and EDNRB genes were screened for genetic variation by semi-automated bi-directional sequencing analysis and matched to controls.

MAIN RESULTS

Male:female ratio (3:1) had a female proband in 4 families. Aganglionosis was significantly more frequent with total colonic aganglionosis (TCA) in 40% familial cases (viz: 17/43 (43%) vs. 19/342 non-familial patients (5.6%) (p<0.01)). Transmission of S-HSCR was observed in 13 (31%), which was associated with EDNRB variation. RET gene promoter variation correlated with extended aganglionosis in 6/35 kindreds (17%). In 3 kindreds, both significant EDNRB and RET mutations were identified and where present were associated with increased penetrance in succeeding generations. An increased penetrance with succeeding generations occurred in 6 (14%). In a further 3 generation family, extensive variations in exon 6, 13, and 18 affected 3 males with progressive penetration and aganglionic length, including total intestinal aganglionosis in the further offspring. RET and MEN association was noted in 5 kindreds (14.3%) related to RET variations at Cysteine sites.

CONCLUSIONS

Cumulative effects of the RET and EDNRB genes contribute to long-segment and total colonic aganglionosis.

Chromosomal and related Mendelian syndromes associated with Hirschsprung's disease

Hirschsprung's disease (HSCR) is a fairly frequent cause of intestinal obstruction in children. It is characterized as a sex-linked heterogonous disorder with variable severity and incomplete penetrance giving rise to a variable pattern of inheritance. Although Hirschsprung's disease occurs as an isolated phenotype in at least 70% of cases, it is not infrequently associated with a number of congenital abnormalities and associated syndromes, demonstrating a spectrum of congenital anomalies. Certain of these syndromic phenotypes have been linked to distinct genetic sites, indicating underlying genetic associations of the disease and probable gene-gene interaction, in its pathogenesis. These associations with HSCR include Down's syndrome and other chromosomal anomalies, Waardenburg syndrome and other Dominant sensorineural deafness, the Congenital Central Hypoventilation and Mowat-Wilson and other brain-related syndromes, as well as the MEN2 and other tumour associations. A number of other autosomal recessive syndromes include the Shah-Waardenburg, the Bardet-Biedl and Cartilage-hair hypoplasia, Goldberg-Shprintzen syndromes and other syndromes related to cholesterol and fat metabolism among others. The genetics of Hirschsprung's disease are highly complex with the majority of known genetic sites relating to the main susceptibility pathways (RET an EDNRB). Non-syndromic non-familial, short-segment HSCR appears to represent a non-Mendelian condition with variable expression and sex-dependent penetrance. Syndromic and familial forms, on the other hand, have complex patterns of inheritance and being reported as autosomal dominant, recessive and polygenic patterns of inheritance. The phenotypic variability and incomplete penetrance observed in Hirschsprung's disease could also be explained by the involvement of modifier genes, especially in its syndromic forms. In this review, we look at the chromosomal and Mendelian associations and their underlying signalling pathways, to obtain a better understanding of the pathogenetic mechanisms involved in developing aganglionosis of the distal bowel.

'Hop the skip' with extended segment intestinal biopsy in Hirschsprung's disease

INTRODUCTION

Skip segment Hirschsprung's is an extremely rare condition, with only 25 reported cases in the English language literature. Diagnosis of skip segment Hirschsprung's may be missed as it is rarely suspected at initial surgery.

PRESENTATION OF CASE

A case report of an infant with total colonic aganglionosis and a skip segment Hirschsprung's in the cecum is presented. A review of literature on current surgical practice is presented along with our suggested modification to the diagnostic and therapeutic algorithm of this rare condition.

DISCUSSION

In our patient the initial leveling colostomy was incorrectly sited at the level of the first detected ganglionated segment. Subsequent recurrent episodes of enterocolitis led to a diagnosis of a long skip segment involving the ascending colon, cecum and terminal ileum. Correct leveling colostomy and a subsequent Duhamel procedure led to a good outcome.

CONCLUSION

Determination of the transition zone in Hirschsprung's may be incorrect if intestinal biopsies are terminated at the first evidence of ganglion cells. Extended segment intestinal biopsies should be included in the algorithm for management of long segment Hirschsprung's disease and will enable the surgeon to correctly detect rare manifestations such as skip segment disease at the initial procedure.