Guanidinoacetate methyltransferase deficiency

Alternative names	Guanidinoacetate methyltransferase deficiency GAMT deficiency Creatinine deficiency syndrome
About the condition	GAMT deficiency is a very rare condition that results in impaired conversion of guanidinoacetate (GAA) to creatine. The decreased creatine impairs the body’s ability to use and store energy effectively, which primarily affects brain and muscles. GAA accumulates in the body and can have toxic effects on the brain.
Inheritance	Autosomal recessive
Year screening started in WA	2025
Incidence in Australia	Currently unknown
Enzyme defect	Deficiency of the enzyme guanidinoacetate methyltransferase
Symptoms if untreated	Developmental delay Seizures Impaired speech Hypotonia Movement disorders Behavioural changes
Metabolites on bloodspot screening	Increased guanidinoacetate (GAA)
Diagnostic tests	Plasma guanidinoacetate and creatine Plasma creatine GAMT gene analysis
Treatment	Studies indicate that children diagnosed early and treated before symptoms appear are more likely to remain healthy and have normal development Creatine supplementation Low protein diet Ornithine supplementation
Screening issues	None