SLC25A15 and Hyperornithinemia: Hyperornithinemia-Hyperammonemia-Homocitrullinuria (HHH) syndrome (Phenotype MIM number 238970) is a rare genetic disease of the urea cycle caused by disease-causing variants in the Solute Carrier Family 25, Member 15 gene; SLC25A15 (alias Ornithine Transporter, Mitochondrial, one; ORNT1, gene MIM number 603861) (Camacho et al., 1999; Tsujino et al., 2000; Salvi et al., 2001; Martinelli et al., 2015).