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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 delays, especially in speech development; intellectual disabilities; and decreased muscle tone (hypotonia) soon after birth. Communication problems may improve over time in people with this disorder.

About half of people with succinic semialdehyde dehydrogenase deficiency 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. Other behavioral and psychiatric features, including aggression and obsessive-compulsive disorder (OCD), tend to develop in adolescence and early adulthood. 


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


Variants (also called 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.

ALDH5A1 gene variants lead to a shortage (deficiency) of succinic semialdehyde dehydrogenase. This deficiency results in an increase in the amount of GABA and a related molecule called gamma-hydroxybutyrate (GHB) in the body, which affects the brain. It is unclear how an increase in GABA and GHB causes developmental delays, seizures, and other signs and symptoms of succinic semialdehyde dehydrogenase deficiency.


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

Other Names for This Condition

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

Additional Information & Resources

Genetic and Rare Diseases Information Center

Patient Support and Advocacy Resources

Clinical Trials

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed


  • 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. doi: 10.1002/humu.10288. Citation on PubMed
  • 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. doi: 10.1016/s0006-3223(03)00113-6. Citation on PubMed
  • 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. doi: 10.1007/s10545-005-7053-4. Citation on PubMed
  • Gordon N. Succinic semialdehyde dehydrogenase deficiency (SSADH) (4-hydroxybutyric aciduria, gamma-hydroxybutyric aciduria). Eur J Paediatr Neurol. 2004;8(5):261-5. doi: 10.1016/j.ejpn.2004.06.004. Citation on PubMed
  • Pearl PL, DiBacco ML, Papadelis C, Opladen T, Hanson E, Roullet JB, Gibson KM. Succinic Semialdehyde Dehydrogenase Deficiency: Review of the Natural History Study. J Child Neurol. 2021 Nov;36(13-14):1153-1161. doi: 10.1177/0883073820981262. Epub 2021 Jan 4. Citation on PubMed
  • 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. doi: 10.1212/01.wnl.0000059549.70717.80. Citation on PubMed
  • 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. doi: 10.1002/ana.10629. Citation on PubMed
  • Pearl PL, Taylor JL, Trzcinski S, Sokohl A. The pediatric neurotransmitter disorders. J Child Neurol. 2007 May;22(5):606-16. doi: 10.1177/0883073807302619. Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.