Table 1 The different types of non-ketotic hyperglycinemia
Forms of NKH | Criteria | |
|---|---|---|
* Classic NKH | Primary GCE-deficiencies due to pathogenic variants in one of the GCE protein components, the P protein (GLDC gene) or the T protein (AMT gene) | |
 1) Severe NKH |  | - Neonatal epileptic encephalopathy and transient coma for two to three weeks - Minimal developmental progress - Spasticity - Therapy-resistant epilepsy |
 2) Attenuated NKH |  | It may present in the neonatal period with a similar transient comatose episode, but may also present later during infancy. |
a) Poor | - Children usually suffer from epilepsy - Very limited development (DQ < 20) - Only sitting or at best only walking a few steps - No or very limited speech | |
b) Intermediate | - Marked development (DQ 20-50) - No or treatable epilepsy - Frequently encounter marked behavioral problems | |
c) Good | - Marked development (DQ >50) - No or treatable epilepsy - Frequently encounter marked behavioral problems | |
* Variant NKH | Caused by pathogenic variants in other genes with an effect on GCE | |