NCIt definition : An autosomal recessive disorder of creatine synthesis caused by mutations(s) in the
GAMT gene on chromosome 19p13, encoding guanidinoacetate N-methyltransferase. It is
characterized by developmental delay/regression, mental retardation, severe disturbance
of expressive and cognitive speech, intractable seizures and movement disturbances,
severe depletion of creatine/phosphocreatine in the brain, and accumulation of guanidinoacetic
acid (GAA) in brain and body fluids.;