Currently, eight subtypes of UCDs are recognized: argininosuccinate lyase deficiency (ASLD), ornithine transcarbamylase deficiency (OTCD), N-acetylglutamate synthase deficiency (NAGSD), carbamoylphosphate synthetase 1 deficiency (CPS1D), argininosuccinate synthetase deficiency (ASSD), arginase 1 deficiency (ARG1D), hyperornithinaemia-hyperammonaemia-homocitrullinuria syndrome (HHHS), and citrin deficiency (Citrin D) [3]. The gene discussed is SLC25A13; the disease is hyperammonemia due to N-acetylglutamate synthase deficiency.