NBS may detect distal UCDs (citrullinemia type 1 or argininosuccinate synthetase deficiency [ASSD, OMIM #215700], argininosuccinic aciduria or argininosuccinate lyase deficiency [ASLD, OMIM #207900] and arginase 1 deficiency or argininemia [ARG1D, OMIM #207800]), and citrullinemia type 2 or citrin deficiency (Citrin-D, OMIM #605814 and #603471), a mitochondrial transport defect of the urea cycle. Here, ARG1 is linked to citrullinemia type I.