Type I citrullinemia (CTLN1, OMIM# 2,15,700) is caused by argininosuccinate synthase 1 gene (ASS1) mutations, while type II citrullinemia is caused by citrin gene (SLC25A13) mutations (Woo et al., 2014). The gene discussed is SLC25A13; the disease is citrullinemia type I.