Arginine:glycine amidinotransferase deficiency (Orphanet_35704) can be described as follows. L-Arginine:glycine amidinotransferase (AGAT) deficiency is an autosomal recessive disorder of creatine biosynthesis (see this term) described in 7 patients to date and characterized by a mild to moderate intellectual disability, usually without pyramidal/extrapyramidal and behavioral problems. Early diagnosis and treatment with oral doses of creatine monohydrate supplementation appears successful in the prevention of AGAT deficiency manifestations.