North American usage: mental retardation.
Guanidinoacetate methyltransferase (GAMT) deficiency: late onset of movement disorder and preserved expressive language
Article first published online: 6 JAN 2009
© The Authors. Journal compilation © Mac Keith Press 2008
Developmental Medicine & Child Neurology
Volume 51, Issue 5, pages 404–407, May 2009
How to Cite
O’ROURKE, D. J., RYAN, S., SALOMONS, G., JAKOBS, C., MONAVARI, A. and KING, M. D. (2009), Guanidinoacetate methyltransferase (GAMT) deficiency: late onset of movement disorder and preserved expressive language. Developmental Medicine & Child Neurology, 51: 404–407. doi: 10.1111/j.1469-8749.2008.03227.x
- Issue published online: 6 APR 2009
- Article first published online: 6 JAN 2009
- PUBLICATION DATA Accepted for publication 12th October 2008. Published online 6th January 2009.
Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine biosynthesis, characterized by early-onset learning disability and epilepsy in most affected children. Severe expressive language delay is a constant feature even in the mildest clinical phenotypes. We report the clinical, biochemical, imaging, and treatment data of two female siblings (18y and 13y) with an unusual phenotype of GAMT deficiency. The oldest sibling had subacute onset of a movement disorder at age 17 years, later than has been previously reported. The younger sibling had better language skills than previously described in this disorder. After treatment with creatine, arginine restriction and ornithine-supplemented diet, seizure severity and movement disorder were reduced but cognition did not improve. This report confirms that GAMT deficiency, a heterogeneous, potentially treatable disorder, detected by increased levels of guanidinoacetate in body fluids (e.g. plasma or urine) or by an abnormal creatine peak on magnetic resonance spectroscopy, should be considered in patients of any age with unexplained, apparently static learning disability and epilepsy.