Whole exome sequencing (WES) presented no genomic variants that accounted for Leigh syndrome, except heterozygous mutations in maternal c.832G > A, p.(Ala278Thr) in ECHS1. In silico analysis predicted this variant to be pathogenic (Supplementary Table 4: SIFT, 0; Polyphen-2, 0.985; CADD, 23; REVEL, 0.389; Mutation Assessor, 0.938; and Mutation Taster, 0.999). This evidence concerns the gene ECHS1 and Leigh syndrome.