Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome: A Case Report of an Uncommon Condition

The megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS), also known as Berdon syndrome, is a rare congenital condition that falls within the spectrum of visceral myopathies. It is characterized by the presence of megacystis, microcolon, and hypoperistalsis, which are secondary to gastrointestinal and urinary system dysmotility. It is frequently associated with other alterations in the gastrointestinal and genitourinary tracts. Although it is possible to make the diagnosis in the prenatal period, most cases are diagnosed after birth through genetic and imaging studies. Advances in treatment have led to a progressive increase in survival rates. We present the case of a newborn with congenital alterations described prenatally and with imaging findings characteristic of the syndrome.

Histopathological, Ultrastructural, and Immunohistochemical Findings in MYH11-Variant Visceral Myopathy

BACKGROUND

Pathogenic mutations in the smooth muscle myosin heavy chain gene, MYH11, cause megacystis megacolon intestinal hypoperistalsis syndrome and other forms of chronic intestinal pseudo-obstruction. Evaluation of intestinal tissues from affected patients is often performed before mutational analysis, but the pathological findings of MYH11-variant visceral myopathy have not been well defined.

METHODS

Light microscopic, immunohistochemical, and ultrastructural findings from multiple intestinal samples from 2 patients with MYH11-variant visceral myopathy were reviewed, including MYH11-specific immunohistochemistry. The findings were compared with intestinal samples from patients with gamma-smooth muscle actin (ACTG2)-variant visceral myopathy and non-pseudo-obstruction controls.

RESULTS

Apart from non-specific changes (e.g., muscle hypertrophy and distension-related muscularis propria necrosis), no alterations were identified by routine histopathological evaluation or electron microscopy. Immunohistochemistry with antibodies against a battery of smooth muscle proteins, including MYH11, revealed indistinguishable patterns of immunoreactivity in the muscularis propria of both patients and controls.

CONCLUSIONS

Myopathic morphological or immunohistochemical changes may not be present in intestinal specimens from patients with MYH11-variant visceral myopathy. Molecular genetic studies should be considered for patients with chronic intestinal pseudo-obstruction and normal or non-specific pathology findings.

Heterozygous Actg2R257C mice mimic the phenotype of megacystis microcolon intestinal hypoperistalsis syndrome

BACKGROUND

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare and serious congenital disorder with poor outcomes, where a heterozygous missense mutation is present in the ACTG2 gene. Here, we aimed to investigate the pathogenesis of ACTG2 in MMIHS.

METHODS

A cohort with 20 patients with MMIHS was screened. Actg2^R257C heterozygous mutant mice were generated using the CRISPR/Cas9 system. Gastrointestinal (GI) motility, voluntary urination, collagen gel contraction, and G-actin/F-actin analysis were performed.

KEY RESULTS

The R257C variant of ACTG2 most frequently occurred in patients with MMIHS and demonstrated the typical symptoms of MMIHS. Actg2^R257C heterozygous mutant mice had dilated intestines and bladders. The functional assay showed a prolonged total time of GI transit and decreased urine spot area. Collagen gel contraction assay and G-actin/F-actin analysis indicated that mutant mice showed reduced area of contraction of smooth muscle cells (SMCs) and impaired actin polymerization.

CONCLUSIONS & INFERENCES

A mouse model demonstrating MMIHS-like symptoms was generated. The Actg2^R257C heterozygous variant impairs SMCs contraction by interfering with actin polymerization, leading to GI motility disorders.

Autosomal Recessive ACTG2-Related Visceral Myopathy in Brothers

Pediatric intestinal pseudo-obstruction (PIPO) is a heterogeneous condition characterized by impaired gastrointestinal propulsion, a broad clinical spectrum, and variable severity. Several molecular bases underlying primary PIPO have been identified, of which autosomal dominant ACTG2-related visceral myopathy is the most common in both familial or sporadic primary PIPO cases. We present a family with autosomal recessive ACTG2-related disease in which both parents have mild gastrointestinal symptoms and sons have severe PIPO and bladder dysfunction.

Methods

Clinical genome sequencing was performed on the patients and the mother. Immunohistochemistry was performed on intestinal tissue from the patients to show expression levels of the ACTG2.

Results

Genome sequencing identified a 6.8 kb 2p13.1 loss that includes the ACTG2 gene and a maternally inherited missense variant p.Val10Met in the ACTG2 gene.

Discussion

This case demonstrates that monoallelic hypomorphic ACTG2 variants may underly mild primary gastrointestinal symptoms, while biallelic mild variants can cause severe diseases. The Deletions of the noncoding ACTG2 exon can be an under-recognized cause of mild gastrointestinal symptoms unidentifiable by exome sequencing, explaining some instances of interfamilial variability with an apparent autosomal dominant inheritance. Genome sequencing is recommended as a genetic work-up for primary or idiopathic PIPO because of genetic heterogeneity.

Japanese clinical practice guidelines for allied disorders of Hirschsprung's disease, 2017

BACKGROUND

Despite the presence of ganglion cells in the rectum, some patients have symptoms similar to those of Hirschsprung's disease. A consensus has yet to be established regarding the terminology for these diseases. We defined this group of diseases as "allied disorders of Hirschsprung's disease" and compiled these guidelines to facilitate accurate clinician diagnosis and provide appropriate treatment strategies for each disease.

METHODS

These guidelines were developed using the methodologies in the Medical Information Network Distribution System (MINDS). Of seven allied disorders, isolated hypoganglionosis; megacystis-microcolon-intestinal hypoperistalsis syndrome; and chronic idiopathic intestinal pseudo-obstruction were selected as targets of clinical questions (CQ). In a comprehensive search of the Japanese- and English-language articles in PubMed and Ichu-Shi Web, 836 pieces of evidence related to the CQ were extracted from 288 articles; these pieces of evidence were summarized in an evidence table.

RESULTS

We herein outline the newly established Japanese clinical practice guidelines for allied disorders of Hirschsprung's disease. Given that the target diseases are rare and intractable, most evidence was drawn from case reports and case series. In the CQ, the diagnosis, medication, nutritional support, surgical therapy, and prognosis for each disease are given. We emphasize the importance of full-thickness intestinal biopsy specimens for the histopathological evaluation of enteric ganglia. Considering the practicality of the guidelines, the recommendations for each CQ were created with protracted discussions among specialists.

CONCLUSIONS

Clinical practice recommendations for allied disorders of Hirschprung's disease are given for each CQ, along with an assessment of the current evidence. We hope that the information will be helpful in daily practice and future studies.

The incidence and outcome of allied disorders of Hirschsprung's disease in Japan: Results from a nationwide survey. Asian J Surg. 2017;40:29-34. [PMID: 26216257 DOI: 10.1016/j.asjsur.2015.04.004]

BACKGROUND

Allied disorders of Hirschsprung's disease (ADHD) have been proposed to be the concept of the functional obstruction of the intestine with the presence of ganglion cells in the terminal rectum. They are classified into two categories based on pathology: (1) abnormal ganglia, including immaturity of ganglia, hypoganglionosis (HG), and intestinal neuronal dysplasia; (2) normal ganglia, including megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS), segmental dilatation (SD), internal anal sphincter achalasia (IASA), and chronic idiopathic intestinal pseudo-obstruction (CIIP). Some of these show poor prognosis, therefore, the establishment of criteria and appropriate treatment strategies is required.

METHODS

The questionnaires were sent to the 161 major institutes of pediatric surgery or gastroenterology in Japan, in order to collect the cases of ADHD during 10 years from 2001 and 2010.

RESULTS

In total, 355 cases were collected. They included 28 immaturity of ganglia, 130 HG (121 congenital, 9 acquired), 18 intestinal neuronal dysplasia, 33 MMIHS, 43 SD, three IASA, and 100 CIIP. Of the 95 institutes, 69 (72.6%) had their own criteria for ADHD. Criteria were based on clinical symptoms and signs, and conventional pathological examinations. Prognosis was poor in congenital HG, MMIHS, and CIIP, while the others showed good survival rates.

CONCLUSION

Almost all Japanese cases of ADHD in the past 10 years were collected. Congenital HG and CIIP showed relatively high incidence, whereas acquired HG and IASA were extremely rare in Japan. The criteria of each disorder were also collected and summarized. Prognosis was poor in congenital HG, MMIHS, and CIIP.