# An atypical presentation in a child with propionic acidemia? Better think twice!

## TL;DR

An infant with propionic acidemia showed unusual symptoms, leading to the discovery of a second genetic disorder affecting brain energy metabolism.

## Contribution

Identifies a rare co-occurrence of propionic acidemia and SLC19A3-related thiamine metabolism dysfunction syndrome 2.

## Key findings

- The child exhibited atypical neurological and metabolic symptoms not typical of propionic acidemia alone.
- Rapid trio exome sequencing revealed a second genetic disorder contributing to the clinical presentation.
- The combined pathomechanisms of both disorders impair brain energy metabolism and lead to overlapping clinical features.

## Abstract

This report details the case of an infant with confirmed propionic acidemia who presented with progressive neurological deterioration and recurrent episodes of metabolic decompensation with elevated lactate levels, but without hyperammonemia. The child's clinical course and neuroradiological findings increasingly deviated from the known clinical and neuroradiological spectrum of propionic acidemia. A rapid trio exome sequencing identified SLC19A3‐related thiamine metabolism dysfunction syndrome 2 as a second genetic disease. The pathomechanisms of both diseases synergize in the impairment of brain energy metabolism, and the associated clinical phenotypes partially overlap, which explains the severe and atypical course of propionic acidemia in the reported case.