Glycine Metabolism Disorders

Nonketotic hyperglycinemia (605899*)

Glycine cleavage enzyme systemGlycine cleavage enzyme system

Biochemical profile: Elevated plasma and cerebrospinal fluid glycineElevated plasma and cerebrospinal fluid glycine

Clinical features: In fetuses, severe hiccups

In neonatal form, severe hiccups, hypotonia, seizures, myoclonus, apnea, death

In infantile and episodic forms, seizures, intellectual disability, episodic delirium, chorea, vertical gaze palsy

In late-onset form, progressive spastic diplegia, optic atrophy, but no cognitive impairment or seizures

Treatment: No effective treatment; in some patients, temporary benefit from sodium benzoate and dextromethorphan No effective treatment; in some patients, temporary benefit from sodium benzoate and dextromethorphan

In some patients with specific mutations, benefit from cofactor therapy with pyridoxine (GLDC mutations) or folinic acid (AMT mutations)In some patients with specific mutations, benefit from cofactor therapy with pyridoxine (GLDC mutations) or folinic acid (AMT mutations)

P protein

H protein

T protein

L protein