Brain MRI features in late-onset nonketotic hyperglycinemia

Achados de RM de crânio na hiperglicinemia não-cetótica de início tardio

A 22-year-old woman presented with learning disability and gait unsteadiness since adolescence. Medical history revealed episodes of encephalopathy and myoclonic jerks associated with intercurrent infections. Examination showed spastic paraparesis, ataxia and optic atrophy. Neuroimaging revealed agenesis of corpus callosum (Figure). Plasma amino acid analysis disclosed elevated glycine levels with an increased cerebrospinal fluid:plasma glycine ratio.

Figure
Neuroimaging findings in nonketotic hyperglycinemia. Sagittal and axial brain MR images disclosing nearly complete corpus callosum agenesis (sparing only a small portion of the genu) and interhemispheric connection by posterior commissure (white arrow) in T1-weighted (A, B), T2-weighted (C) and FLAIR (D) sequences. Putamina, anterior commissure and hemispheric supratentorial white matter are also thin.

Nonketotic hyperglycinemia (MIM #605899) is an autosomal recessive disorder of glycine metabolism caused by a defect in the glycine cleavage system with three different clinical forms: neonatal, infantile and late-onset with heterogeneous brain malformations, such as abnormal corpus callosum, gyral malformations and enlarged ventricles¹,².

References

• ¹
  Hoover-Fong JE, Shah S, Van Hove JLK, Applegarth D, Toone J, Hamosh A. Natural history of nonketotic hyperglycinemia in 65 patients. Neurology. 2004;63(10):1847-53. doi:10.1212/01.WNL.0000144270.83080.29
• ²
  Dobyns WB. Agenesis of the corpus callosum and gyral malformations are frequent manifestations of nonketotic hyperglycinemia. Neurology. 1989;39(6):817-20. doi:10.1212/WNL.39.6.817

Publication Dates

• Publication in this collection
  Oct 2015

History

• Received
  30 Mar 2015
• Reviewed
  09 June 2015
• Accepted
  29 June 2015