A total of 104 patients from 98 different families were included, with the following diagnosis: 67 OTC deficiency (64.4%), 22 ASS deficiency (type 1 citrullinemia) (21.1%), 10 ASL deficiency (argininosuccinic aciduria) (9.6%), 2 CPS1 deficiency (1.92%), 2 ARG1 deficiency (1.92%) and 1 NAGS deficiency (0.96%). The gene discussed is ARG1; the disease is hyperammonemia due to N-acetylglutamate synthase deficiency.