Haack et al (Annals of Clinical and Translational Neurology, 2015, 2 (5) pp. 492-509) recently reported a disorder of encephalopathy, deafness, optic atrophy, and cardiomyopathy caused by mutations in short-chain enoyl-CoA hydratase  (ECHS1). This mitochondrial matrix enzyme functions in the oxidation of fatty acids and some amino acids (particularly valine). Patients present with a wide range of clinical severity, and an apparently moderate impairment of fatty acid oxidation compared to the severity clinical features. Therefore, the authors postulate that the impairment in amino acid oxidation contributes significantly to the phenotype.

This disorder should be suspected in an individual with the above clinical features and urine organic acid findings of increased ethylmalonate and 2-methyl-2,3 dihydroxybutyrate.

Hilary Vernon, MD PhD