The purpose of this study is to conduct post-marketing surveillance of carglumic acid (Carbaglu) to obtain long-term clinical safety information. Carglumic acid was approved by the United States Food and Drug Administration (FDA) for treatment of acute hyperammonemia due to N-acetylglutamate synthase (NAGS) deficiency. Much of the FDA-required data is already collected through the Longitudinal Study of Urea Cycle Disorders (RDCRN Protocol #5101). This study will collect additional data on adverse events (interim events), adverse reactions, pregnancy, and fetal outcomes.