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Reviewed August 2009

What is hyperlysinemia?

Hyperlysinemia is an inherited condition characterized by elevated blood levels of the amino acid lysine, a building block of most proteins. Hyperlysinemia is caused by the shortage (deficiency) of the enzyme that breaks down lysine. Hyperlysinemia typically causes no health problems, and most people with elevated lysine levels are unaware that they have this condition. Rarely, people with hyperlysinemia have intellectual disability or behavioral problems. It is not clear whether these problems are due to hyperlysinemia or another cause.

How common is hyperlysinemia?

The incidence of hyperlysinemia is unknown.

What genes are related to hyperlysinemia?

Mutations in the AASS gene cause hyperlysinemia. The AASS gene provides instructions for making an enzyme called aminoadipic semialdehyde synthase. This enzyme performs two functions in the breakdown of lysine. First, the enzyme breaks down lysine to a molecule called saccharopine. It then breaks down saccharopine to a molecule called alpha-aminoadipate semialdehyde.

Mutations in the AASS gene that impair the breakdown of lysine result in elevated levels of lysine in the blood and urine. These increased levels of lysine do not appear to have any negative effects on the body.

When mutations in the AASS gene impair the breakdown of saccharopine, this molecule builds up in blood and urine. This buildup is sometimes referred to as saccharopinuria, which is considered to be a variant of hyperlysinemia. It is unclear if saccharopinuria causes any symptoms.

Read more about the AASS gene.

How do people inherit hyperlysinemia?

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

Where can I find information about diagnosis or management of hyperlysinemia?

These resources address the diagnosis or management of hyperlysinemia and may include treatment providers.

You might also find information on the diagnosis or management of hyperlysinemia in Educational resources and Patient support.

General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.

To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.

Where can I find additional information about hyperlysinemia?

You may find the following resources about hyperlysinemia helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for hyperlysinemia?

  • alpha-aminoadipic semialdehyde deficiency disease
  • familial hyperlysinemia
  • lysine alpha-ketoglutarate reductase deficiency disease
  • saccharopine dehydrogenase deficiency disease
  • saccharopinuria

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about hyperlysinemia?

Where can I find general information about genetic conditions?

What glossary definitions help with understanding hyperlysinemia?

amino acid ; autosomal ; autosomal recessive ; breakdown ; cell ; deficiency ; dehydrogenase ; disability ; enzyme ; familial ; gene ; incidence ; inherited ; lysine ; molecule ; newborn screening ; recessive ; screening

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.

References (3 links)


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.

Reviewed: August 2009
Published: February 8, 2016