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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Succinic semialdehyde dehydrogenase deficiency

Reviewed June 2008

What is succinic semialdehyde dehydrogenase deficiency?

Succinic semialdehyde dehydrogenase deficiency is a disorder that can cause a variety of neurological problems. People with this condition typically have developmental delay, especially involving speech development; intellectual disability; and decreased muscle tone (hypotonia) soon after birth. About half of those affected experience seizures, difficulty coordinating movements (ataxia), decreased reflexes (hyporeflexia), and behavioral problems. The most common behavioral problems associated with this condition are sleep disturbances, hyperactivity, difficulty maintaining attention, and anxiety. Less frequently, affected individuals may have increased aggression, hallucinations, obsessive-compulsive disorder (OCD), and self-injurious behavior, including biting and head banging. People with this condition can also have problems controlling eye movements. Less common features of succinic semialdehyde dehydrogenase deficiency include uncontrollable movements of the limbs (choreoathetosis), involuntary tensing of the muscles (dystonia), muscle twitches (myoclonus), and a progressive worsening of ataxia.

How common is succinic semialdehyde dehydrogenase deficiency?

Approximately 350 people with succinic semialdehyde dehydrogenase deficiency have been reported worldwide.

What genes are related to succinic semialdehyde dehydrogenase deficiency?

Mutations in the ALDH5A1 gene cause succinic semialdehyde dehydrogenase deficiency. The ALDH5A1 gene provides instructions for producing the succinic semialdehyde dehydrogenase enzyme. This enzyme is involved in the breakdown of a chemical that transmits signals in the brain (neurotransmitter) called gamma-amino butyric acid (GABA). The primary role of GABA is to prevent the brain from being overloaded with too many signals.

A shortage (deficiency) of succinic semialdehyde dehydrogenase leads to an increase in the amount of GABA and a related molecule called gamma-hydroxybutyrate (GHB) in the body, particularly the brain and spinal cord (central nervous system). It is unclear how an increase in GABA and GHB causes developmental delay, seizures, and other signs and symptoms of succinic semialdehyde dehydrogenase deficiency.

Related Gene(s)

Changes in this gene are associated with succinic semialdehyde dehydrogenase deficiency.

  • ALDH5A1

How do people inherit succinic semialdehyde dehydrogenase deficiency?

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 succinic semialdehyde dehydrogenase deficiency?

These resources address the diagnosis or management of succinic semialdehyde dehydrogenase deficiency and may include treatment providers.

  • Gene Review: Succinic Semialdehyde Dehydrogenase Deficiency (
  • Genetic Testing Registry: Succinate-semialdehyde dehydrogenase deficiency (
  • MedlinePlus Encyclopedia: Hyperactivity (

You might also find information on the diagnosis or management of succinic semialdehyde dehydrogenase deficiency 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 succinic semialdehyde dehydrogenase deficiency?

You may find the following resources about succinic semialdehyde dehydrogenase deficiency 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 succinic semialdehyde dehydrogenase deficiency?

  • 4-hydroxybutyricaciduria
  • 4-hydroxybutyric aciduria
  • Gamma-hydroxybutyric acidemia
  • gamma-hydroxybutyric aciduria
  • SSADH deficiency

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 succinic semialdehyde dehydrogenase deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding succinic semialdehyde dehydrogenase deficiency?

aciduria ; anxiety ; ataxia ; autosomal ; autosomal recessive ; breakdown ; cell ; central nervous system ; decreased muscle tone ; deficiency ; dehydrogenase ; developmental delay ; disability ; dystonia ; enzyme ; GABA ; gene ; hallucinations ; hyperactivity ; hypotonia ; inherited ; involuntary ; molecule ; muscle tone ; myoclonus ; nervous system ; neurological ; obsessive-compulsive disorder ; OCD ; recessive

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


  • Akaboshi S, Hogema BM, Novelletto A, Malaspina P, Salomons GS, Maropoulos GD, Jakobs C, Grompe M, Gibson KM. Mutational spectrum of the succinate semialdehyde dehydrogenase (ALDH5A1) gene and functional analysis of 27 novel disease-causing mutations in patients with SSADH deficiency. Hum Mutat. 2003 Dec;22(6):442-50. (
  • Gibson KM, Gupta M, Pearl PL, Tuchman M, Vezina LG, Snead OC 3rd, Smit LM, Jakobs C. Significant behavioral disturbances in succinic semialdehyde dehydrogenase (SSADH) deficiency (gamma-hydroxybutyric aciduria). Biol Psychiatry. 2003 Oct 1;54(7):763-8. (
  • Gibson KM. Gamma-hydroxybutyric aciduria: a biochemist's education from a heritable disorder of GABA metabolism. J Inherit Metab Dis. 2005;28(3):247-65. (
  • Gordon N. Succinic semialdehyde dehydrogenase deficiency (SSADH) (4-hydroxybutyric aciduria, gamma-hydroxybutyric aciduria). Eur J Paediatr Neurol. 2004;8(5):261-5. Review. (
  • Pearl PL, Gibson KM, Acosta MT, Vezina LG, Theodore WH, Rogawski MA, Novotny EJ, Gropman A, Conry JA, Berry GT, Tuchman M. Clinical spectrum of succinic semialdehyde dehydrogenase deficiency. Neurology. 2003 May 13;60(9):1413-7. (
  • Pearl PL, Novotny EJ, Acosta MT, Jakobs C, Gibson KM. Succinic semialdehyde dehydrogenase deficiency in children and adults. Ann Neurol. 2003;54 Suppl 6:S73-80. Review. (
  • Pearl PL, Taylor JL, Trzcinski S, Sokohl A. The pediatric neurotransmitter disorders. J Child Neurol. 2007 May;22(5):606-16. Review. (


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: June 2008
Published: February 8, 2016