Recurrent Liver Failure in an 11-Year-Old Boy

Hepatic Form of Dihydrolipoamide Dehydrogenase Deficiency (DLDD): Phenotypic Spectrum, Laboratory Findings, and Therapeutic Approaches in 52 Patients

Dihydrolipoamide dehydrogenase deficiency (MIM 246900/DLDD) is an autosomal recessive mitochondrial disease with three clinical subgroups. The hepatic form leads to recurrent metabolic decompensations often accompanied by elevated levels of liver transaminases (ELT) in blood, sometimes progressing to acute liver failure (ALF). Genetically, it is linked to the p.G229C variant in the DLD gene, which has been reported in the Ashkenazi Jewish and Arabic population. In this study, we analyzed phenotypic diversity, therapeutic management, and outcome in novel symptomatic individuals with hepatic DLDD identified by whole exome sequencing (n = 7) in Central Europe as well as in previously reported cases (n = 45). Fifty-one of 52 DLDD patients carried the p.G229C variant (39 in a homozygous state). During decompensations, precipitated by febrile infectious disease or fasting, affected individuals presented with nausea, vomiting, abdominal pain, hepatomegaly, hypoglycemia, and lactic acidosis. In individuals homozygous for the p.G229C variant, neurologic manifestations were rare, whereas mild neurologic symptoms were found in individuals (n = 8) carrying a different DLD variant in trans. During decompensation, levels of specific plasma amino acids like citrulline or branched-chain amino acids, and urinary organic acids, like 2-oxoglutaric acid, were frequently elevated. However, known biomarkers-with the exception of lactate-were not consistently elevated during these episodes and typically normal in the interval, highlighting the usefulness of early genetic testing in all children with unexplained ELT or ALF to reduce the time to diagnosis. While there exists consensus for rescue therapy with intravenous glucose during decompensations and maintenance therapy with riboflavin, therapies with thiamine and antioxidants (e.g., N-acetylcysteine) were reported to be useful in single individuals with recurrent decompensations.

Dihydrolipoamide dehydrogenase deficiency in two unrelated Tunisian children

BACKGROUND

Dihydrolipoamide dehydrogenase deficiency (DLDD) (OMIM# 246,900) is an extremely rare inherited metabolic disorder causing neurological and/or liver impairment. The clinical manifestations are mostly characterized by severe neurological impairment in early childhood, hepatic presentations and rarely by myopathic manifestations.

CASE PRESENTATIONS

Here, we describe two patients presenting with recurrent episodes of vomiting and liver dysfunction. DLDD was confirmed via sanger sequencing by identification of the pathogenic variant c.685G > T (p.Gly229Cys) in DLD gene at a homozygous state.

CONCLUSION

To our knowledge, this is the first Tunisian report of DLDD. Phenotypic spectrum of this disease is very large. Biochemical markers that predict the impairment of the pathways affected by the deficiency of E3 subunit (gluconeogenesis, tricyclic cycle and catabolism of branched chain aminoacids) are variably present. Confirmation is based on genetic study of DLD gene.

Dihydrolipoamide dehydrogenase, pyruvate oxidation, and acetylation-dependent mechanisms intersecting drug iatrogenesis

In human metabolism, pyruvate dehydrogenase complex (PDC) is one of the most intricate and large multimeric protein systems representing a central hub for cellular homeostasis. The worldwide used antiepileptic drug valproic acid (VPA) may potentially induce teratogenicity or a mild to severe hepatic toxicity, where the underlying mechanisms are not completely understood. This work aims to clarify the mechanisms that intersect VPA-related iatrogenic effects to PDC-associated dihydrolipoamide dehydrogenase (DLD; E3) activity. DLD is also a key enzyme of α-ketoglutarate dehydrogenase, branched-chain α-keto acid dehydrogenase, α-ketoadipate dehydrogenase, and the glycine decarboxylase complexes. The molecular effects of VPA will be reviewed underlining the data that sustain a potential interaction with DLD. The drug-associated effects on lipoic acid-related complexes activity may induce alterations on the flux of metabolites through tricarboxylic acid cycle, branched-chain amino acid oxidation, glycine metabolism and other cellular acetyl-CoA-connected reactions. The biotransformation of VPA involves its complete β-oxidation in mitochondria causing an imbalance on energy homeostasis. The drug consequences as histone deacetylase inhibitor and thus gene expression modulator have also been recognized. The mitochondrial localization of PDC is unequivocal, but its presence and function in the nucleus were also demonstrated, generating acetyl-CoA, crucial for histone acetylation. Bridging metabolism and epigenetics, this review gathers the evidence of VPA-induced interference with DLD or PDC functions, mainly in animal and cellular models, and highlights the uncharted in human. The consequences of this interaction may have significant impact either in mitochondrial or in nuclear acetyl-CoA-dependent processes.