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Non-ketotic Hyperglycinaemia
Short Description : Non-ketotic Hyperglycinaemia Genetic Testing
Also known as : [Glycine encephalopathy],[NKH]

Test performed by: LabPLUS - Dept. Diagnostic Genetics - Molecular Genetics

Referral Requirements

Important Note:

Requires referral through Metabolic or Genetics Services.

Predictive/carrier testing through Genetic Services only.


Genetic Health Service NZ can be contacted on 0800 476 123.

Specimen Collection
EDTA8 mL Adult EDTA Blood
EDTA4 mL Paediatric EDTA Blood


For paediatric samples a minimum of 0.5ml blood EDTA can be processed. (Microcollect)

Transport all bloods at room temperature within 24-48 hours. If necessary specimens can be refrigerated overnight for transport at room temperature the following day.

For testing of other sample types please contact the laboratory prior to sending.

Turnaround Time: Within 13 weeks
Contact Information

Contact Molecular Genetics via:

Lablink                                                     ext 22000

Mark Greenslade (Technical Head)   ext 22010

Pippa Grainger (Section leader)              ext 22014

Email: DGen@adhb.govt.nz

Background Information

Glycine encephalopathy (also known as nonketotic hyperglycinemia, NKH) is an inborn error of glycine metabolism in which large quantities of glycine accumulate in all body tissues, including the brain. A neonatal (classic) form and several atypical forms exist. The vast majority of individuals with NKH have the neonatal (classic) form; a minority of individuals with NKH have atypical forms. The neonatal form manifests in the first hours to days of life with progressive lethargy, hypotonia, and myoclonic jerks leading to apnea and often death. Surviving infants develop profound mental retardation and intractable seizures. The atypical forms range from infantile- to late-onset milder disease to late-onset disease with a rapid and severe course. The infantile form is characterized by onset of seizures beyond the neonatal period. The developmental outcome may be better than in the neonatal form, but does not exceed moderate mental retardation. The mild-episodic form of glycine encephalopathy is associated with mild mental retardation and episodes of chorea, agitated delirium, and vertical gaze palsy. The late-onset form has variable mild spastic paraparesis, optic atrophy, mild mental retardation, and choreoathetosis.

The three genes known to be associated with glycine encephalopathy are: GLDC (encoding the P-protein component of the GCS complex and accounting for 70%-75% of disease), AMT (encoding the T-protein component of the GCS complex and accounting for ~20% of disease), and GCSH (encoding the H-protein component of the GCS complex and accounting for <1% of disease). About 5% of persons with-enzyme proven NKH do not have a mutation in any of these three genes.

Molecular genetic testing for GLDC  is available.

For more information about the Molecular Genetics service:

Molecular Genetics information page

Last updated at 15:49:04 22/03/2021