# Poster Session I - A38 MEGACYSTIS-MICROCOLON-INTESTINAL HYPOPERISTALSIS SYNDROME (MMIHS): A RARE CASE WITH FULL CLINICAL EXPRESSION

## TL;DR

This paper presents a rare case of a genetic disorder affecting the bladder and intestines, highlighting the need for early diagnosis and multidisciplinary care.

## Contribution

The paper reports a rare case of MYH11-related MMIHS with full clinical features and emphasizes its diagnostic and management challenges.

## Key findings

- A homozygous pathogenic MYH11 variant was identified in a patient with MMIHS.
- The case demonstrates the need for multidisciplinary care to manage complex symptoms and improve outcomes.
- Early recognition and intervention are critical for better survival and quality of life in MMIHS.

## Abstract

Megacystis Microcolon Intestinal Hypoperistalsis Syndrome (MMIHS) is a rare congenital disorder characterized by a triad of dilated urinary bladder (megacystis), microcolon, and intestinal hypoperistalsis due to myopathic dysfunction of the bowel and bladder. Mutations in genes such as ACTG2 and MYH11 have been implicated. Although the condition was historically fatal, advances in intestinal rehabilitation and transplantation have improved survival and outcomes

Presentation of a rare case of MYH11-related syndrome with full clinical features, and to expound its potential clinical implications, diagnostic challenges, and implications of multidisciplinary care

Case report and literature review

An eight-month-old girl was born at 37 weeks’ gestation to consanguineous parents. Family history revealed similar findings in two pregnancies of a maternal aunt and one prior pregnancy of the mother, all undiagnosed. Antenatal ultrasound at 21 weeks was suggestive of duodenal atresia, renal pelvic dilation, and megacystis with polyhydramnios. Amniocentesis and whole-exome sequencing confirmed a homozygous pathogenic MYH11 variant (c.3424C>T; p.R1142*), diagnostic of autosomal recessive MMIHS.

Baby was born with APGAR scores (3-6-7) and was intubated immediately. Urinary catheter was inserted at 6 hours of age due to anuria. Imaging confirmed duodenal stenosis, absent peristalsis, microcolon and severe bilateral hydronephrosis. The patient underwent multiple surgical procedures. Initial exploration at six days of age revealed multiple intestinal stenoses and malrotation, and an end jejunostomy and mucous fistula were created. Due to persistent functional obstruction further exploration revealed the bowel to have multiple stenotic, but patent segments. There was no peristalsis. Her colon contained thick mucous plugs. A PEG tube was placed.

Her urological course was marked by grade IV vesicoureteral reflux and recurrent urinary tract infections despite prophylactic antibiotics, requiring a vesicostomy at 6 months of age to relieve bladder distension and to facilitate drainage. She currently has CKD stage 2, Cystatin C (GFR 70 ml/min/1.73 m2). She remains dependent on total parenteral nutrition, with weight tracking at the 3rd centile and stable liver function

This case highlights the complexity of MMIHS and the importance of early, ideally prenatal, recognition. Despite advances in intestinal rehabilitation and transplantation improving survival, optimal outcomes still require intensive multidisciplinary care and individualized planning

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