Abstract: Dihydrolipoamide dehydrogenase (DLD) deficiency is an autosomal recessive metabolic disorder characterized by an unpredictable pattern of presentation and a wide phenotypic spectrum. DLD is a common constituent of multiple mitochondrial complexes. It is also known as E3 (dihydrolipoamide: NAD+ oxidoreductase, EC 1.8.1.4). DLD, encoded by the DLD gene, is vital for catalysis. Thus, genetically induced deficiency of the enzyme, although very rare, is associated with failure to thrive, hypotonia, and metabolic acidosis [1,2].  In this report, we present the case of a 12-year-old Lebanese boy with a homozygous mutation in the DLD gene: c.685G>T p. Gly229Cys, who presented with liver failure, hyperammonemia, and encephalopathy. Genetic testing of his sibling revealed homozygosity for the same pathogenic variant.