ORC1 and urea cycle disorder: Mutations in the solute carrier family 25 member 15 (SLC25A15) gene, which encodes for ORC1, are causative of the rare autosomal recessive urea cycle disorder (UCD) called hyperornithinemia–hyperammonemia–homocitrullinuria (HHH) syndrome (OMIM 238970) (1, 5).