[(1)H] magnetic resonance spectroscopy of urine: diagnosis of a guanidinoacetate methyl transferase deficiency case

For the first time, the use or urine [H-1] magnetic resonance spectroscopy has allowed the detection of 1 case of guanidinoacetate methyl transferase in a database sample of 1500 pediatric patients with a diagnosis of central nervous system impairment of unknown origin. The urine [H-1] magnetic resonance spectroscopy of a 9-year-old child, having severe epilepsy and nonprogressive mental and motor retardation with no apparent cause, revealed a possible guanidinoacetic acid increase. The definitive assignment of guanidinoacetic acid was checked by addition of pure substance to the urine sample and by measuring [H-1]-[H-1] correlation spectroscopy. Diagnosis of guanidinoacetate methyl transferase deficiency was further confirmed by liquid chromatography-mass spectrometry, brain [H-1] magnetic resonance spectroscopy, and Mutational analysis of the guanidinoacetate methyl transferase gene. The replacement therapy was promptly started and, after 1 year, the child was seizure free. We conclude that for this case, Urine [H-1] magnetic resonance spectroscopy screening was able to diagnose guanidinoacetate methyl transferase deficiency.