ASS1 and ornithine carbamoyltransferase deficiency: This includes 5 enzymatic deficiencies directly affecting the urea cycle: carbamoyl-phosphate synthetase 1 deficiency (CPS1D), ornithine transcarbamylase deficiency (OTCD), argininosuccinate synthetase 1 deficiency (ASS1D-citrullinemia type 1), argininosuccinate lyase deficiency (ASLD-argininosuccinic aciduria), and arginase 1 deficiency (ARG1D).