Non-ketotic hyperglycinemia (NKH) is a rare, genetic, metabolic disorder caused by a defect in the enzyme system that breaks down the amino acid glycine, resulting in an accumulation of glycine in the body’s tissues and fluids.

What is NKH life expectancy?

It is possible that up to 30% of babies with the severe neonatal form of nonketotic hyperglycinemia (NKH) will pass away shortly after birth. Those that survive generally have severe seizures and profound intellectual disability.

What is non-ketotic hyperglycinemia?

Nonketotic hyperglycinemia is a disorder characterized by abnormally high levels of a molecule called glycine in the body (hyperglycinemia). The excess glycine builds up in tissues and organs, particularly the brain.

Is hyperglycinemia autosomal recessive or dominant?

Nonketotic hyperglycinemia is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Typically, the parents of an individual with the condition each carry one copy of the mutated gene, but they usually do not show signs and symptoms of the condition.

What are the signs and symptoms of attenuated nonketotic hyperglycinemia?

The signs and symptoms of the attenuated form of nonketotic hyperglycinemia are similar to, but milder than, those of the severe form of the condition. Children with attenuated nonketotic hyperglycinemia typically reach developmental milestones, although the skills they achieve vary widely.

How is hyperglycemic hyperactivity treated in patients with glycine toxicity?

Hyperactivity or chorea may be seen in these patients. Treatment involves benzoate to lower glycine levels and using drugs to block the NMDA receptors which are stimulated by glycine. Prognosis in the attenuated cases is highly variable. Constance Smith-Hicks, Gerald V. Raymond, in Cerebrospinal Fluid in Clinical Practice, 2009