Guanidinoacetate methyltransferase, deficiency in

[MIM 612 736]

Prevalence : < 1.106. Autosomal recessive transmission of a mutation of the GAMT gene( 19p13.3). GAMT is a liver enzyme that transforms the guanidinoacetic acid in creatine. Its deficiency causes a lack of creatine in brain and muscle. This deficiency can lead to secondary abnormalities of the mitochondrial respiratory chain and thus a wrong diagnosis of mitochondrial cytopathy.

Symptoms: first signs between 3 months and 3 years ; delayed speech (deficit in expressive speech)  and learning, autistic traits, epilepsy, hyperactivity, extrapyramidal movements (chorea, athetosis, ataxia).

Diagnosis: low levels of plasma creatine; MRI: increase of the signal at the level of the globus pallidus.

Treatment: nutritional supplements in creatine (100 - 700 mg/kg/day in 3 6 doses) and a low-protein diet (low in Arginine but enriched with ornithine) result in clinical improvement (abnormal movements, epilepsy).


Anesthetic implications: 

epilepsy, hyperactivity, autistic behavior


References : 

-        Gordon N. 
Guanidinoacetate methyltransferase deficiciency (GAMT). 
Brain & Development 2010; 32: 79-81.


Updated: April 2019