Glycine encephalopathy

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Glycine encephalopathy
Synonyms	Non-ketotic hyperglycinemia
Pronounce
Specialty	Neurology, Genetics
Symptoms	Seizures, hypotonia, lethargy, developmental delay
Complications	N/A
Onset	Neonatal period
Duration	Lifelong
Types	N/A
Causes	Genetic mutation
Risks	Family history
Diagnosis	Genetic testing, CSF/plasma glycine ratio
Differential diagnosis	Ketotic hyperglycinemia, Urea cycle disorder
Prevention	N/A
Treatment	Sodium benzoate, dextromethorphan, antiepileptic drugs
Medication	N/A
Prognosis	Variable, often poor
Frequency	Rare
Deaths	N/A

Glycine encephalopathy

Glycine encephalopathy, also known as non-ketotic hyperglycinemia, is a rare genetic disorder characterized by an accumulation of the amino acid glycine in the body, particularly affecting the central nervous system. This condition is caused by a defect in the glycine cleavage system, which is responsible for breaking down glycine in the body.

Pathophysiology

Glycine encephalopathy is primarily caused by mutations in the genes that encode the components of the glycine cleavage system. This system is composed of four protein components: P-protein, T-protein, H-protein, and L-protein. Mutations in the GLDC gene, which encodes the P-protein, are the most common cause of the disorder. The accumulation of glycine in the brain leads to neurological symptoms due to its role as an inhibitory neurotransmitter.

Clinical Features

The clinical presentation of glycine encephalopathy can vary, but it typically includes severe neurological symptoms. These may include:

• Hypotonia (reduced muscle tone)
• Seizures
• Developmental delay
• Lethargy
• Apnea

The severity of symptoms can range from mild to severe, with the most severe cases presenting in the neonatal period.

Diagnosis

Diagnosis of glycine encephalopathy is based on clinical features, biochemical testing, and genetic analysis. Elevated levels of glycine in the blood and cerebrospinal fluid (CSF) are indicative of the disorder. Genetic testing can confirm mutations in the genes associated with the glycine cleavage system.

Treatment

There is currently no cure for glycine encephalopathy. Treatment is primarily supportive and may include:

• Anticonvulsants to manage seizures
• Sodium benzoate to reduce glycine levels
• Physical therapy and occupational therapy to support development

Prognosis

The prognosis for individuals with glycine encephalopathy varies depending on the severity of the condition. Severe forms of the disorder are associated with significant neurological impairment and reduced life expectancy. Milder forms may allow for a longer lifespan with varying degrees of disability.

See also

• Genetic disorder
• Amino acid
• Neurotransmitter
• Seizure disorder