P042: California's experience with guanidinoacetate methyltransferase enzyme newborn screening on the first 100,000 samples

Guanidinoacetate methyltransferase enzyme (GAMT) deficiency is a rare, inherited metabolic disorder that affects the synthesis of creatine. Creatine is an essential metabolite for regenerating energy, particularly in the brain and muscles. Creatine is synthesized from guanidinoacetate (GUAC) by the GAMT enzyme. Variants in the GAMT gene result in a shortage of the GAMT enzyme that causes a deficiency of creatine and accumulation of GUAC in the body, which is a neurotoxin. Newborn screening for GAMT was recently initiated in California using a two-tier approach for the detection of GAMT biomarkers (GUAC, creatine and creatinine) in newborn dried blood spots (DBS).