TARS2 and epilepsy: Biallelic pathogenic variants in TARS2 cause combined oxidative phosphorylation deficiency 21 (COXPD21), which is a rare mitochondrial encephalomyopathy characterized by early-onset severe axial hypotonia, limb hypertonia, delayed psychomotor development, epilepsy, brain anomalies and increased serum lactate level, often leading to early death; onset after 6 months results in a milder course and longer survival [1].