Journal of Inherited Metabolic Disease

, Volume 30, Issue 1, pp 100–100

Guanidinoacetate methyltransferase deficiency masquerading as a mitochondrial encephalopathy

Authors

    • Willink UnitRoyal Manchester Children’s Hospital
  • R. E. Appleton
    • Department of NeurologyRoyal Liverpool Children’s Hospital
  • B. Power
    • Department of NeurologyRoyal Liverpool Children’s Hospital
  • D. M. Isherwood
    • Department of BiochemistryRoyal Liverpool Children’s Hospital
  • L. J. Abernethy
    • Department of RadiologyRoyal Liverpool Children’s Hospital
  • R. W. Taylor
    • Mitochondrial Research Group, School of Neurology, Neurobiology and PsychiatryUniversity of Newcastle upon Tyne
  • D. M. Turnbull
    • Mitochondrial Research Group, School of Neurology, Neurobiology and PsychiatryUniversity of Newcastle upon Tyne
  • N. M. Verhoeven
    • Department of Clinical Chemistry, Metabolic UnitVU University Medical Center
  • G. S. Salomons
    • Department of Clinical Chemistry, Metabolic UnitVU University Medical Center
  • C. Jakobs
    • Department of Clinical Chemistry, Metabolic UnitVU University Medical Center
Short Report

DOI: 10.1007/s10545-006-0478-2

Cite this article as:
Morris, A.A.M., Appleton, R.E., Power, B. et al. J Inherit Metab Dis (2007) 30: 100. doi:10.1007/s10545-006-0478-2

Summary

Guanidinoacetate methyltransferase (GAMT) deficiency is a rare disorder of creatine synthesis. We report a patient who presented at 10 months of age with hypotonia and global developmental delay. Subsequently, she developed seizures and choreoathetosis. Magnetic resonance imaging showed high signal bilaterally in the globus pallidus on T2-weighted images. Mitochondrial respiratory chain studies revealed low complex I activity (in muscle 0.052 nmol NADH oxidized per min per unit citrate synthase, controls 0.166 ± 0.047; in fibroblasts 0.080 nmol NADH oxidized per min per unit citrate synthase, controls 0.197 ± 0.034). The true diagnosis was suspected at 21 months of age because of persistent low plasma and urine creatinine concentrations. GAMT activity was undetectable in fibroblasts and compound heterozygous mutations were found in the GAMT gene (c.327G>A and c.522G>A). The patient was treated with creatine, dietary arginine restriction and ornithine supplements. Her movement disorder and seizures resolved but she still has severe cognitive impairment and no expressive language. The occurrence of secondary respiratory chain abnormalities in GAMT deficiency may lead to misdiagnosis, particularly as the clinical and radiological features resemble those seen in mitochondrial encephalopathies. It is important to establish the correct diagnosis because specific treatment is available.

Supplementary material

10545_2006_ESM_478.pdf (241 kb)
Guanidinoacetate methyltransferase deficiency masquerading as a mitochondrial encephalopathy

Copyright information

© SSIEM and Springer 2006