ARGININE:GLYCINE AMIDINOTRANSFERASE DEFICIENCY: A TREATABLE METABOLIC ENCEPHALOMYOPATHY

Abstract

Creatine and creatine phosphate are essential for intracellular storage and utilization of phosphate-bound energy. Aside from dietary sources, creatine is chiefly synthesized in liver in a 2-step enzymatic process (arginine:glycine amidinotransferase [AGAT] and guanidinoacetate methyltransferase), is carried via blood to target organs, and then transported using creatine transporter–1 into the tissues. Creatine deficiency syndromes related to each of the 2 enzymatic steps and creatine transporter–1 have been recently reported in patients with developmental delay and mental retardation.1 We report adult cases of myopathy in AGAT deficiency. ### Case reports. #### Case IV-30. A 26-year-old Jordanian woman was born full-term to first-cousin parents (figure). She had moderate developmental delay in childhood; she began walking at age 20 months and speaking in monosyllables at age 6 years. At adolescence, she had impaired fine motor skills and speech difficulty but was independent in activities of daily living. Figure Brain creatine levels in arginine:glycine amidinotransferase (AGAT) deficiency (A) Pedigree chart showing consanguinity. (B, C) 1H magnetic resonance spectroscopy in IV-30 showing low creatine peaks (arrows) and …