ARG1 and arginase deficiency: Mutations in the arginase 1 (ARG1) gene cause arginase deficiency, a rare autosomal recessive metabolic disorder.57 Arginase deficiency disrupts the urea cycle, causing ammonia accumulation and clinical manifestations (e.g. headaches, hypo/hyperventilation, seizures, coma and even death).58 Current treatment involves dietary modification, which mainly treats symptoms, without sufficiently preventing cognitive abnormalities.59