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Adenylosuccinate Lyase Deficiency (ASLD)

Last updated April 26, 2018

Approved by: Maulik P. Purohit MD, MPH

Adenylosuccinate Lyase Deficiency (ASLD) is a rare genetic disorder characterized by adenlyosuccinate lyase enzyme deficiency.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Adenylosuccinase Deficiency
  • Adenylosuccinate Deficiency
  • ADSL Deficiency

What is Adenylosuccinate Lyase Deficiency? (Definition/Background Information)

  • Adenylosuccinate Lyase Deficiency (ASLD) is a rare genetic disorder characterized by adenlyosuccinate lyase enzyme deficiency
  • When such a deficiency occurs, the individual may have signs and symptoms similar to autism, improper/poor functioning of the muscles, psychological symptoms, and convulsions
  • ASLD is caused by mutations in the adenylosuccinate lyase (ADSL) gene that are inherited in an autosomal recessive pattern. It can be diagnosed through a genetic test
  • Presently, there is no treatment for Adenylosuccinate Lyase Deficiency, though medications help improve the quality of life. The prognosis of the condition is generally grim

Who gets Adenylosuccinate Lyase Deficiency? (Age and Sex Distribution)

  • Adenylosuccinate Lyase Deficiency is normally diagnosed during infancy. The symptoms are usually seen within the first year of life
  • Individuals of all ages and both genders are affected by ASLD
  • Individuals of all race/ethnic background are prone to the condition

What are the Risk Factors for Adenylosuccinate Lyase Deficiency? (Predisposing Factors)

  • Inherited genetic defects are the most important risk factors of Adenylosuccinate Lyase Deficiency. Thus, individuals with a positive family history are at an increased risk for the same

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Adenylosuccinate Lyase Deficiency? (Etiology)

  • Adenylosuccinate Lyase Deficiency is caused by mutations in the adenylosuccinate lyase (ADSL) gene on chromosome 22q
  • In many cases, these mutations are passed down through families in an autosomal recessive pattern
  • The mutations that have been so far identified, have all shown to cause structural instability in the enzyme

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Adenylosuccinate Lyase Deficiency?

Signs and symptoms can vary greatly amongst individuals with Adenylosuccinate Lyase Deficiency. Some of these include:

  • Signs and symptoms  that are similar to autism
  • Psychomotor retardation
  • Epilepsy, seizures
  • Growth impairment
  • Muscle degeneration, low muscle tone and tension results in overall muscular weakness
  • Feeding problems, which includes difficulties in feeding

How is Adenylosuccinate Lyase Deficiency Diagnosed?

A diagnosis of Adenylosuccinate Lyase Deficiency would involve:

  • Physical exam with evaluation of family medical history
  • Genetic testing: By studying an individual’s DNA, mutations on the ADSL gene that cause ASLD can be identified and a diagnosis made

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Adenylosuccinate Lyase Deficiency?

Complications due to Adenylosuccinate Lyase Deficiency are commonly noted and may include:

  • Short-stature,severe growth failure
  • Abnormal physical features, such as small head circumference, flat occiput (back of the skull), small nose, thin upper lip, low set ears, etc.
  • Learning disabilities, learning may be slow with accompanying language delays

How is Adenylosuccinate Lyase Deficiency Treated?

Currently, there are no curative/definitive treatment options for Adenylosuccinate Lyase Deficiency. The treatment measures are taken to improve the quality of life by addressing the variety of signs and symptoms.

  • Some individuals have been given oral supplements of adenine and allopurinol, to ease the symptoms
  • Therapeutic trials with ribose and uridine are being implemented, though their effectiveness in reducing the symptoms are yet to be established

How can Adenylosuccinate Lyase Deficiency be Prevented?

  • Currently there are no specific methods or guidelines to prevent Adenylosuccinate Lyase Deficiency, which is a genetic condition
  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks prior to planning for a child
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis of Adenylosuccinate Lyase Deficiency? (Outcomes/Resolutions)

The prognosis of individuals with Adenylosuccinate Lyase Deficiency is generally unpredictable and grim. Most individuals die in their early infancy or during childhood.

Additional and Relevant Useful Information for Adenylosuccinate Lyase Deficiency:

A defect in the adenlyosuccinate lyase enzyme is detected, if the presence of certain proteins, such as succinylaminoimidazole carboxamide riboside and succinyladenosine, are detected in the cerebrospinal fluid, urine, and blood plasma. Such a positive test indicates a mutation in the ADSL gene. However, DNA testing is the definitive method for diagnosis of Adenylosuccinate Lyase Deficiency.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Dec. 17, 2013
Last updated: April 26, 2018