# Atypical MEGDHEL Syndrome: A Milder Phenotype With Hepatic Presentation and Failure to Thrive Associated With a Homozygous Nonsense Variant of SERAC1

## TL;DR

A 3-year-old boy with a rare genetic disorder showed milder symptoms, including liver issues and poor growth, due to a specific gene variant.

## Contribution

Reports an atypical MEGDHEL syndrome case with a novel clinical presentation and a specific SERAC1 gene variant.

## Key findings

- The patient had elevated liver enzymes and steatosis without neurological symptoms.
- A homozygous nonsense variant in SERAC1 (p.Y259*) was identified as the cause.
- Mitochondrial dysfunction was observed with reduced complex activity and mild mtDNA depletion.

## Abstract

MEGDHEL syndrome, caused by a SERAC1 gene defect, is clinically defined as the association of 3‐MGA‐uria (MEG), deafness (D), hepatopathy (H), encephalopathy (E), and Leigh‐like features (L). Clinical presentation typically begins in the neonatal period, with neurological symptoms becoming more evident by 2 years of age. Severe liver involvement has also been reported. We report the case of a 3‐year‐old boy with increased transaminases and failure to thrive of unknown cause. He was born prematurely at 35 weeks and needed neonatal intensive care support for 24 h due to transient tachypnea. At 18 months, laboratory investigations for failure to thrive revealed elevated transaminases without cholestasis, which persisted on subsequent evaluations. Abdominal wall collateral veins were found during physical examination, and the liver ultrasound revealed steatosis, prompting the decision to proceed with a liver biopsy. Common causes of chronic liver disease were ruled out. Following liver biopsy, performed under general anesthesia, he had an episode of unexplained decompensation (metabolic acidosis, hyperlactatemia, and 3‐methylglutaconic aciduria). The aciduria persisted upon subsequent evaluation. Liver histology showed macro/microvesicular steatosis (25%), portal tract inflammation, and mild fibrosis. Cardiac evaluation, along with brain magnetic resonance imaging and spectroscopy, was normal. Further investigations revealed decreased hepatic activity of respiratory mitochondrial chain complexes and marginal mtDNA depletion (28.1%). Analysis of the SERAC1 gene showed homozygosity for p.Y259* (c.777T>G, exon 9). This case report raises awareness for an atypical presentation of MEGDHEL syndrome associated with a homozygous nonsense variant of SERAC1 clinically characterized by mild hypertransaminasemia, failure to thrive, no neurological involvement, and starting in early childhood rather than infancy.