Neonatal encephalocardiomyopathy caused by mutations in VARS2.

VARS2 encodes a mitochondrial aminoacyl-tRNA-synthetase. Mutations in VARS2 have recently been identified as a cause of mitochondrial encephalomyopathy in three individuals. However, clinical information remained scarce. Exome sequencing lead us to identify compound heterozygous pathogenic VARS2 variants in a boy presenting with severe lactic acidosis, hypertrophic cardiomyopathy, epilepsy, and abnormalities on brain imaging including hypoplasia of corpus callosum and cerebellum as well as a massive lactate peak on MR-spectroscopy. Studies in patient-derived fibroblasts confirmed the functional relevance of the identified VARS2 variants. Our report expands the phenotypic spectrum associated with this rare mitochondrial defect, in that VARS2 deficiency may also cause severe neonatal presentations with cardiac involvement and structural brain abnormalities.