Glycine synthase deficiency

Glycine Synthase Deficiency is a rare metabolic disorder characterized by an inability to break down and process the amino acid glycine due to a deficiency in the enzyme glycine synthase. This condition is also known as glycine encephalopathy or non-ketotic hyperglycinemia (NKH). Glycine is a simple, non-essential amino acid that plays a crucial role in various biochemical pathways within the body, including the synthesis of proteins, the production of glutathione (a powerful antioxidant), and neurotransmission.

Causes

Glycine synthase deficiency is caused by mutations in the genes responsible for the production of the glycine cleavage system (GCS), particularly the AMT, GLDC, and GCSH genes. These mutations lead to a functional impairment or total absence of the GCS enzyme complex, which is essential for the catabolism of glycine. The condition is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected.

Symptoms

The symptoms of glycine synthase deficiency typically manifest shortly after birth and can include severe neurological disorders, hypotonia (reduced muscle tone), seizures, apnea (breathing difficulties), intellectual disability, and developmental delay. The severity of symptoms can vary widely among affected individuals. In some cases, symptoms may be so severe that they lead to death in infancy or early childhood.

Diagnosis

Diagnosis of glycine synthase deficiency involves a combination of clinical evaluation, biochemical tests, and genetic testing. Biochemical tests measure the levels of glycine in the blood and cerebrospinal fluid (CSF), with elevated levels being indicative of the disorder. Genetic testing can confirm the diagnosis by identifying mutations in the genes associated with the condition.

Treatment

There is currently no cure for glycine synthase deficiency, and treatment focuses on managing symptoms and preventing complications. Treatment options may include dietary management to restrict glycine intake, medications to control seizures, and in some cases, the administration of sodium benzoate to reduce glycine levels in the body. Early intervention and a multidisciplinary approach to care are crucial for improving the quality of life for affected individuals.

Prognosis

The prognosis for individuals with glycine synthase deficiency varies depending on the severity of the condition and the effectiveness of the treatment regimen. While some individuals may experience significant developmental delays and lifelong disabilities, others, with milder forms of the disorder and effective management, may achieve better developmental outcomes.

Glycine synthase deficiency Resources
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