Genetische Grundlagen des Morbus Hirschsprung

OUR EXPERIENCE IN TREATMENT OF HIRSCHSPRUNG'S DISEASE IN A 18-YEAR-OLD PATIENT. CLINICAL CASE

Introduction: Hirschsprung's disease (HD) is a relatively rare condition, in which the intermuscular (Auerbach) and submucosal (Meissner) plexus are absent in the colon wall at various lengths. In the literature, HD is described mainly in relation to the pediatric surgery area of interests because up to 90% of cases of this disease are detected before the age of 5 years 6. However, in some patients, the symptoms of the disease are not severe, so patients survive to adulthood without an established diagnosis.Clinical case: we demonstrate our experience of surgical treatment of Hirschsprung's disease in a 18-year-old patient.Conclusion: Although Hirschsprung's disease is in most cases a disease of childhood, it is necessary to keep in mind its typical symptoms when an adult patient complains of constipation. Proper diagnosis and correctly selected surgical treatment can not only eliminate symptoms and improve quality of life, but also reduce the likelihood of serious complications.

Intronic RET gene variants in Down syndrome-associated Hirschsprung disease in an African population

BACKGROUND

Clinical association between Hirschsprung disease (HD) and Down syndrome (DS) is well established. RET promoter and intron 1 variations have been shown to interfere with RET function, increasing the risk of HD pathogenesis. The intronic single-nucleotide polymorphism 2 (SNP2 [rs2435357]) has been associated with DS-associated HD (DS-HD). This study focuses on variations of specific RET intron, 1 SNPs (viz, SNP1 [rs2506004] and SNP2 [rs2435357]) in DS-HD.

PATIENTS AND METHODS

DNA was extracted from paraffin-embedded tissue samples and whole blood in 14 patients with DS with histologically proven HD. Polymerase chain reaction products of RET intron 1 were screened for genetic variation and matched to DS and controls from the general population.

RESULTS

Thirty-seven blood and/or tissue from 14 patients with DS-HD were investigated. RET intronic variations (SNP1 [rs2506004] or SNP2 [rs2435357]) were detected in all patients. SNP1 was detected in all patients, was heterozygous in 9, and homozygous in 5 samples (all aganglionic and 1 total colonic aganglionosis). SNP2 was absent in 6 patients, heterozygous in 6, and homozygous in 3. Three DS controls had a heterozygous SNP1. Homozygous intronic SNP RET variations were related to aganglionic tissue but not normally ganglionated or transitional zone from the same individual.

CONCLUSIONS

Potential disease-related RET mutations were identified in the intron region in 80% of patients with DS-HD investigated, suggesting a causal relationship. The presence of a homozygous form in the aganglionic tissue probably represents a somatic mutation, which suggests local microenvironmental factors in HD pathogenesis.

Hirschsprung's disease in the neurologically challenged child

BACKGROUND

The association between Hirschsprung's disease (HSCR) and central nervous system (CNS) anomalies and syndromes is interesting because of similar developmental pathways. In addition to associated syndromes (e.g., Trisomy 21), these include brain anomalies, mental retardation and growth, ear and hearing deformities, eye hypoplasia, and craniofacial abnormalities, suggesting an neurocristopathy. This group of patients present with neurological challenges and have special challenges in management especially in the older child and adolescent.

METHODS

We retrospectively investigated 32 patients with significant HSCR-associated neurological challenges out of a local database of 555 HSCRs (6%). Data were analyzed with details of neurological problem, treatment, complications, and mortality. Long-term outcome was assessed clinically.

RESULTS

A total of 32 neurologically challenged children were studied. The male/female ratio was 1.7:1 and all ethnic groups were affected. Abnormalities and syndromes included Down (n = 16) and probable Mowat-Wilson (n = 2) syndromes. Other abnormalities included ophthalmic problems (n = 8), CNS and brain abnormalities (n = 8). Mortality (22%) was mostly related to enterocolitis, particularly in Trisomy 21, ophthalmic problems (n = 8), CNS and brain abnormalities (n = 8). Follow-up age range was 1-34 years (8 years, adolescence and beyond). The outcome was variable, concomitant medical problems were common. Several patients failed to achieve satisfactory continence.

CONCLUSION

The association of neurological difficulties in patients with HSCR presents many challenges. Management could involve the exploration and evaluation of alternative treatment choices.

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

BACKGROUND

Hirschsprung's disease (HSCR) represents a complex disorder of signaling molecules, resulting from the effects of at least 9 known susceptibility genes. Affected families carry 200 times higher risk, but genetic counseling via pedigree analysis is difficult and the significance of genetic variations is unclear. This study evaluated a set of patients affected by HSCR with familial recurrence to evaluate factors of greatest value in genetic counseling.

PATIENTS AND METHODS

One hundred twenty patients with HSCR (including 18 kindreds) were screened for genetic variations of the 2 major susceptibility genes (RET and endothelin B receptor [EDNRB]) and compared with 60 control samples (20 per ethnic group). Familial recurrence patterns were studied for patient sex, pattern of recurrence, presence of associated syndromic features, and genetic features of major susceptibility genes. Polymerase chain reaction and HEX-SSCP analysis were performed on DBA extracted from blood/microdissected tissue samples. SSCP variants were validated and automated sequencing techniques performed on polymerase chain reaction products showing conformational variants in acrylamide gel.

RESULTS

Familial cases had a male-female ratio of 1.5:1, male-to-male transmission (n = 10; 2 father to son), female-to-male transmissions (n = 4; 3 female carriers, female-to-female (n = 4; 2 mother to daughter), and 1 paternal RET deletion-female with very long segment aganglionosis. Increasing gene penetrance occurred in 3 pedigrees. An increased incidence of long segment HSCR was noted in families with recurrence and appeared important. No consistent mendelian trends or specific genetic sites were observed, but 3 suggested autosomal dominant and recessive in a further 3. Identified genetic variations included deletions, frame shifts, and missense mutations, as well as a number of significant single nucleotide polymorphism variations. Transmitted RET mutations occurred in 5 (30%) of 16 kindreds. Splice RET mutation plus variants of exon 17 (973L) affected 2 children with identical total colonic aganglionosis. In a 3-generation family, variations in RET exons 6, 13, and 18 (928) affected 3 male children with increasing penetration to recur as total intestinal aganglionosis in a grandchild.

CONCLUSIONS

Mendelian transmission appears mediated by the RET proto-oncogene. EDNRB mutations suggest haplotypic gene-gene interaction. Genetic counseling remains a challenge in HSCR because of its multfactorial etiology.

RET proto-oncogene testing in infants presenting with Hirschsprung disease identifies 2 new multiple endocrine neoplasia 2A kindreds

BACKGROUND

Multiple endocrine neoplasia 2A (MEN 2A) is a genetic syndrome manifesting as medullary thyroid carcinoma (MTC), hyperparathyroidism, and pheochromocytoma. Multiple endocrine neoplasia 2A results from mutations in the RET proto-oncogene. Hirschsprung disease (HSCR) is a rare manifestation of MEN 2A and has been described in known MEN 2A families.

METHODS

Here we describe 2 MEN 2A families that were only identified after the diagnosis of HSCR.

RESULTS

Kindred 1: A boy presented in infancy with HSCR. Genetic screening revealed a C609Y mutation, which is consistent with MEN 2A. Evaluation of his sister, father, and grandmother revealed the same mutation. All 3 had thyroidectomies demonstrating C-cell hyperplasia. The grandmother had a microscopic focus of MTC. Kindred 2: An infant boy and his sister were diagnosed with HSCR as neonates. Genetic testing demonstrated a C620R gene mutation consistent with MEN 2A. Total thyroidectomies revealed metastatic MTC in the father and C-cell hyperplasia in both children.

CONCLUSIONS

Hirschsprung disease can be the initial presentation of MEN 2A. We strongly recommend that genetic screening be performed in patients presenting with HSCR, looking for the known RET mutations associated with MEN 2A. If a mutation consistent with MEN 2A is detected, genetic screening of all first-degree relatives in the kindred is recommended.