Mitochondrial Disorder in a Child With Brainstem Lesions Mimicking Thiamine Deficiency.

Mitochondrial diseases are among the most common genetic disorders. Known as the "powerhouse" of the cell, mitochondria generate energy via oxidative phosphorylation, a process that involves five enzyme complexes. The MT-ND5 gene, which encodes part of Complex I, is especially prone to mutations and is linked to various mitochondrial disorders. Since mitochondria are concentrated in metabolically active organs such as the brain, heart, liver, muscles, and kidneys, these systems are particularly vulnerable to dysfunction. In the brain, mitochondrial disease symptoms often arise in regions with high metabolic demand, such as the brainstem. Disruptions in oxidative phosphorylation due to nicotinamide adenine dinucleotide (NADH)-ubiquinone oxidoreductase chain 5 (MT-ND5) mutations can prevent energy production from meeting cellular demands, leading to serious neurological consequences. This report describes the neuroimaging and clinical presentation of a child with an MT-ND5 pathogenic variant, highlighting characteristic MRI findings and the diagnostic challenges posed by overlapping features with other metabolic disorders, such as thiamine deficiency.