Metabolic and drug-induced muscle disorders.

PURPOSE OF REVIEW: The inherited disorders of muscle metabolism affect both substrate utilization and the final intramitochondrial oxidation through the Krebs cycle and the respiratory chain. Almost every step of these complex biochemical pathways can be affected by inborn errors, whose expression depends on peculiar tissue-specific or systemic gene expression. This review updates current knowledge in this broad field.

RECENT FINDINGS: New inherited defects are still being discovered, such as the beta-enolase deficiency in glycogenosis type XIII and mutations in the gene encoding an esterase/lipase/thioesterase protein in Chanarin-Dorfman syndrome, a multisystem triglyceride storage disease.

SUMMARY: Therapeutic approaches to the metabolic myopathies are still lagging behind, although remarkable observations have been made on the rare coenzyme Q10 deficiency syndrome. However, transgenic animal models may offer the opportunity both to investigate muscle pathogenesis and explore therapeutic targets. Finally, human myotoxicity may provide novel paradigms for naturally occurring muscle disorders.