RARS2 and pontocerebellar hypoplasia type 6: Pontocerebellar hypoplasia type 6 (PCH6, OMIM #611523) is a mitochondrial encephalopathic epilepsy disease characterized by intractable seizures [24,28–38] and is caused by mutations in the mitochondrial arginyl-tRNA synthetase RARS2. A clinical study reported a reduction in seizure frequency and seizure-related disease morbidity in a small cohort of PCH6 patients treated with the experimental drug EPI-743 [39].