GAMT deficiency can be suspected from clinical findings, although clinical findings are not suggestive of a specific diagnosis. Laboratory testing of plasma and urine will show decreased levels of creatine and increased levels of<unk> . Non-specific elevations of metabolites on urine testing, such as organic acid analysis, that are normalized to creatinine may be observed. For these tests, the excretion of urine metabolites is not elevated, but appears elevated due to unusually low creatinine values. Specific diagnostic testing for GAMT deficiency relies on the measurement of<unk>  and creatine in urine and plasma. Increased levels of<unk>  and decreased levels of creatine can suggest a diagnosis. Confirmatory testing can include enzyme assays to directly measure<unk><unk>  activity or molecular testing of GAMT. Brain magnetic resonance spectroscopy will show decreased levels of creatine, in affected individuals, however this finding is seen in all three cerebral creatine deficiencies, and needs to be followed up to identify the specific defect. Treatment is most effective for GAMT deficiency with early diagnosis, however the non-specific clinical findings mean there is often a delay in diagnosis. Due to the efficacy of treatment and the delay in diagnosis, GAMT deficiency has been a candidate for newborn screening programs. Newborn screening assays measure the amount of<unk>  in a dried blood spot using tandem mass spectrometry. Abnormal results from a newborn screening test still need to be confirmed by testing in plasma or urine. GAMT deficiency was nominated to be included in the list of disorders recommended for screening in the United States in 2016. It was not recommended for inclusion, as studies completed at the time could not demonstrate that a case could be reliably identified in a newborn screening setting. Utah started screening for GAMT deficiency in all newborns in 2015. New York started screening newborns in late 2018, and Michigan planned to start in 2019.
Guanidinoacetate methyltransferase deficiency
Holocarboxylase synthetase deficiency
Carbamoyl phosphate synthetase I deficiency
Ornithine translocase deficiency
2,4 Dienoyl-CoA reductase deficiency
Mevalonate kinase deficiency
Aminoacylase 1 deficiency
Arginine:glycine amidinotransferase deficiency