Mitochondrial disorders of the energy metabolism may be manifested in infant age by hepatic failure. The authors describe the clinical picture of a disease and results of metabolic studies in a 10-week-old infant with progressing encephalomyelopathy, lactate acidosis, impaired cytochrome C oxidase and fuhninant hepatic failure which developed in the boy 4 weeks after the onset of valproic acid treatment. The association with the onset of antiepileptic treatment supports the suspicion that valproic acid can induce fulminant hepatic affection in children with an impaired aktivity of the respiratory chain. In all children with suspected mitochondrial disease administration of drugs containing valproic acid should be carefully considered.

        Key words: fulminant hepatic failure, valproic acid, cytochrome C oxidase