Arginine supplementation in four patients with X-linked creatine transporter defect

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Treatment with oral creatine monohydrate has not shown efficacy in patients with creatine transporter deficiency (CRTR-D). Another therapeutic option proposed is L-arginine, the substrate for the enzyme L-arginine:glycine amidinotransferase (AGAT). We evaluate clinical characteristics and cerebral creatine replenishment after L-arginine therapy in four patients with CRTR-D.

Patients and methods

Four boys with genetically confirmed diagnosis of CRTR-D (ages 9–16 years) were supplemented with L-arginine (0.4 g/kg per day) for a period of 9 months. Treatment efficacy was evaluated by clinical and neuropsychological assessment and determination of creatine signals by brain proton magnetic resonance spectroscopy (1H-MRS).


Epileptic seizures remained well controlled with antiepileptic drugs in three cases, both before and after L-arginine supplementation. Vineland Adaptive Behaviour Scale did not show any change in communication, daily living skills, socialization or motor skills, and a lack of improvement in brain 1H-MRS follow-up was observed. L-Arginine was discontinued at the end of the observation period.


Nine months of L-arginine supplementation did not show effectiveness in the four patients affected with CRTR-D in this protocol.

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