Other characteristic, rare diseases are HyperUricemia, Pulmonary hypertension, Renal failure and Alkalosis (HUPRA) syndrome, which is caused by mutations in the mitochondrial seryl-tRNA synthetase 2 (SARS2) (Belostotsky et al., 2011) and Perrault syndrome, characterised by ovarian dysgenesis and sensorineural hearing loss due to mutations in the mitochondrial histidyl-tRNA synthetase 2 (HARS2) (Pierce et al., 2011) and leucyl-tRNA synthetase 2 (LARS2) (Pierce et al., 2013). Here, HARS2 is linked to pulmonary arterial hypertension.