DARS2 and Leukoencephalopathy: Mutations in two mitochondrial ARSs, namely, DARS2 (mitochondrial aspartyl-tRNA synthetase) and RARS2 (mitochondrial arginyl-tRNA synthetase), have been implicated in leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation (LBSL) (Labauge et al, 2011; Lin et al, 2010; Scheper et al, 2007) and infantile encephalopathy (Edvardson et al, 2007), respectively.