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Condition report · Metabolic

Glycine and Serine Metabolism Disorders

Inherited disorders affecting the breakdown of glycine or the production of serine, two amino acids important for brain development. Some forms respond well to early treatment.

A condition report looks for rare variants known to cause the conditions it covers.

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The 2 conditions we analyse

Glycine Encephalopathy (Non-Ketotic Hyperglycinemia)

Autosomal recessive

Caused by variants in GLDC, AMT or GCSH (and, in an atypical form, SLC6A9), which cause high glycine in the brain and can lead to seizures, low muscle tone and developmental problems.

What a diagnosis changes

Knowing allows treatment with sodium benzoate and dextromethorphan, which can reduce seizures in some forms.

Genes analysed

Also known as

GCE; Glycine synthase deficiency; hyperglycinemia nonketotic; NKA; non-ketotic hyperglycinemia

Includes 6 related subtypes ↓
  • atypical glycine encephalopathy
  • glycine encephalopathy 1
  • glycine encephalopathy 2
  • infantile glycine encephalopathy
  • multiple mitochondrial dysfunctions syndrome 7
  • neonatal glycine encephalopathy
MONDO:0011612Orphanet 407MedGen 155625

Serine Deficiency Disorders

Autosomal recessive

Caused by variants in PHGDH, PSAT1 or PSPH, which block serine production and can cause small head size, seizures and developmental delay.

What a diagnosis changes

Knowing allows serine and glycine supplementation, which can prevent or improve symptoms when started early, including before birth.

Genes analysed

Also known as

serine deficiency

Includes 10 related subtypes ↓
  • 3-phosphoglycerate dehydrogenase deficiency
  • Neu-Laxova syndrome
  • Neu-Laxova syndrome 1
  • Neu-Laxova syndrome 2
  • neu-laxova syndrome due to 3-phosphoserine phosphatase deficiency
  • PHGDH deficiency
  • PSAT deficiency
  • PSPH deficiency
  • serine biosynthesis pathway deficiency, infantile/juvenile form
  • spastic tetraplegia-thin corpus callosum-progressive postnatal microcephaly syndrome
MONDO:0018162Orphanet 35705MedGen 1842451

Limitations

  • GLDC has a closely related pseudogene and deletions or duplications of one or more exons are common, so some disease-causing changes may require copy-number analysis and may be missed.

Other metabolic conditions

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