ELAC2 and mitochondrial disease: Biallelic mutations in the elaC ribonuclease Z 2 (ELAC2) gene cause a rare mitochondrial disease, the main features of which are hypertrophic cardiomyopathy, delayed psychomotor development, and usually death during childhood.1 Only 20 families have been reported with this syndrome.1, –, 3 Neither movement disorders nor psychotic features have been described as part of the spectrum of ELAC2 mutations.