Guanidinoacetate methyltransferase (GAMT) deficiency: outcomes in 48 individuals and recommendations for diagnosis, treatment and monitoring

Mol Genet Metab. 2014 Jan;111(1):16-25. doi: 10.1016/j.ymgme.2013.10.018. Epub 2013 Nov 7.

Abstract

We collected data on 48 patients from 38 families with guanidinoacetate methyltransferase (GAMT) deficiency. Global developmental delay/intellectual disability (DD/ID) with speech/language delay and behavioral problems as the most affected domains was present in 44 participants, with additional epilepsy present in 35 and movement disorder in 13. Treatment regimens included various combinations/dosages of creatine-monohydrate, l-ornithine, sodium benzoate and protein/arginine restricted diets. The median age at treatment initiation was 25.5 and 39 months in patients with mild and moderate DD/ID, respectively, and 11 years in patients with severe DD/ID. Increase of cerebral creatine and decrease of plasma/CSF guanidinoacetate levels were achieved by supplementation with creatine-monohydrate combined with high dosages of l-ornithine and/or an arginine-restricted diet (250 mg/kg/d l-arginine). Therapy was associated with improvement or stabilization of symptoms in all of the symptomatic cases. The 4 patients treated younger than 9 months had normal or almost normal developmental outcomes. One with inconsistent compliance had a borderline IQ at age 8.6 years. An observational GAMT database will be essential to identify the best treatment to reduce plasma guanidinoacetate levels and improve long-term outcomes.

Keywords: Autism; Creatine deficiency; Magnetic resonance spectroscopy; Neurodevelopmental outcome; Speech delay; Treatment evidence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Arginine / metabolism*
  • Arginine / therapeutic use*
  • Brain / metabolism
  • Child
  • Child, Preschool
  • Combined Modality Therapy
  • Creatine / metabolism*
  • Creatine / therapeutic use*
  • Female
  • Glycine / analogs & derivatives*
  • Glycine / blood
  • Glycine / cerebrospinal fluid
  • Guanidinoacetate N-Methyltransferase / deficiency*
  • Guanidinoacetate N-Methyltransferase / metabolism
  • Humans
  • Infant
  • Infant, Newborn
  • Intellectual Disability / metabolism
  • Intellectual Disability / therapy*
  • Language Development Disorders / diagnosis
  • Language Development Disorders / metabolism
  • Language Development Disorders / therapy*
  • Male
  • Middle Aged
  • Movement Disorders / congenital*
  • Movement Disorders / diagnosis
  • Movement Disorders / metabolism
  • Movement Disorders / therapy
  • Ornithine / therapeutic use*
  • Practice Guidelines as Topic
  • Sodium Benzoate / therapeutic use*
  • Treatment Outcome
  • Young Adult

Substances

  • Arginine
  • Ornithine
  • Guanidinoacetate N-Methyltransferase
  • glycocyamine
  • Creatine
  • Sodium Benzoate
  • Glycine

Supplementary concepts

  • Guanidinoacetate methyltransferase deficiency