# Prenatal Diagnosis of ACTG2-Related Megacystis–Microcolon–Intestinal Hypoperistalsis Syndrome—Case Report and Systematic Review

## TL;DR

This paper reports a prenatal case of MMIHS and reviews 18 cases, showing most involve ACTG2 mutations and often lead to pregnancy termination.

## Contribution

The study adds a new prenatal case and systematically reviews prenatally diagnosed MMIHS cases, emphasizing the role of ACTG2 mutations.

## Key findings

- ACTG2 mutations were responsible for 55.6% of the prenatally diagnosed MMIHS cases.
- Most cases (72.2%) presented in the second or third trimester with fetal megacystis.
- 77.8% of the cases resulted in termination of pregnancy.

## Abstract

Background/Objectives: Megacystis–microcolon–intestinal hypoperistalsis syndrome (MMIHS) is characterized by smooth muscle dysfunction and results in severe bladder dilatation and intestinal dysmotility. Prenatal diagnosis is challenging due to the non-specific nature of ultrasound findings and the limitations of current genetic testing. We present a case of persistent fetal megacystis, with genetic testing confirming MMIHS, and a systematic review of prenatally diagnosed cases. Methods: An electronic search of the PubMed, Medline, Web of Science and CORE databases was conducted to identify reports of genetic prenatal diagnoses of MMIHS. The inclusion criteria were cases of prenatally suspected MMIHS with a genetic diagnosis based on prenatal samples. Reports that described neonatal or paediatric cases or lacked clinical details or genetic testing results were excluded, and the clinical details for the included cases were collected. Results: We identified six publications describing 17 cases of MMIHS confirmed on genetic testing. Including our case, 18 cases are described in this manuscript. Most cases (72.2%) presented in the second or third trimester of pregnancy; the majority (55.6%) were due to ACTG2 mutations. All cases had fetal megacystis detected on ultrasound. Five cases (27.8%) also had a known family history of MMIHS. The majority of the cases (77.8%) resulted in the termination of pregnancy. Conclusions: MMIHS is a rare condition with significant morbidity and mortality and prenatal diagnosis remains challenging. ACTG2 mutations are described in over half of these cases. These data contribute to the limited literature on its prenatal presentation and the evolving role of prenatal molecular genetic testing.