Table 8.

Creatine synthesis defects.

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