Table 8: Creatine synthesis defects.

Defective enzyme
or component
Urine Creatine Urine GAA (guanidinoacetate)Creatine/creatinine ratiotreatment

AGAT (arginine : glycine amidinotransferase) Normal(i) Amenable to creatine therapy
GAMT (guanidine acetate methyl transferase) Normal(i) Amenable to creatine therapy;
(ii) Dietary restriction of arginine, with ornithine supplementation
(iii) Antiepileptics may be necessary for seizure control
Creatine transporter Normal (may be slightly increased in males)(i) Antiepileptics for seizure control
(ii) Creatine supplementation is ineffective