Nonketotic hyperglycinemia

Nonketotic hyperglycinemia (glycine encephalopathy)

Pregnant complain
"frequent, continuous, rhythmic jerking of the fetus in utero before birth"
reflecting seizures that begin prenatally

Pathophysiology
- Defect mitochondrial glycine cleavage (GLDC/AMT)→ ↑glycine & ↑NMDAr activity

Presentation
First days w/ lethargy + intractable szs + jerks + hiccups + hypotonia
EEG burst-suppression evolving to hypsarrhythmia

Investigation
- FH
- Check Gluc, Na, Ca, Mg, ABG, lactate
- cEEG
- CSF:plasma glycine ratio, add NH3, lactate, plasma AA, urine organic acids, acylcarnitine profile
- bMRI
> spectroscopy→ glycine peak
> corpus callosum agenesis
- genetic panel

Management
- If persistent szs, treat empiric→ pyridoxine ± pyridoxal-5-phosphate and folinic acid