Argininosuccinate lyase deficiency

It is a rare genetic inherited disorder caused by mutations in the asl gene

What are the other names?

• Argininosuccinate acidemia
• Argininosuccinate aciduria
• Argininosuccinate lyase deficiency
• Argininosuccinate lyase deficiency (argininosuccinic aciduria)
• Argininosuccinic academia
• Argininosuccinic acidemia
• Argininosuccinic aciduria deficiency

How common is it?

It is estimated that more than 15 babies are born with this condition each year in the United States.

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What causes Argininosuccinate lyase deficiency?

Argininosuccinic aciduria is an inherited (genetic) condition that prevents the body from removing ammonia properly. Ammonia is a waste product made when the body breaks down proteins. The body removes ammonia in a process called the urea cycle. Arginosuccinate lyase is an enzyme needed for the urea cycle.

In argininosuccinic aciduria, this enzyme is missing or is not made correctly. If your baby does not make enough working argininosuccinate lyase enzyme, the urea cycle does not work well and ammonia builds up.

High levels of ammonia are very toxic to the body, especially the nervous system and the liver. If untreated, this damage leads to the signs and symptoms of the condition. In severe cases, this condition can lead to coma if not treated early.

What is the screening for Argininosuccinic aciduria?

• Newborn screening for argininosuccinic aciduria is done using a small amount of blood collected from your baby’s heel. To learn more about this process
• During screening, a special machine measures how much of certain substances (called amino acids) are in your baby’s blood.

Amino acids are produced when your body breaks down proteins.

• Babies with argininosuccinic aciduria cannot break down two amino acids called citrulline and argininosuccinic acid.
• Babies with high levels of these substances might have argininosuccinic aciduria.

What are the signs and symptoms?

• Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly.
• It is important to follow their instructions.
• Your baby may need to get treatment right away, even if they are not showing signs or symptoms.
• In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.

Signs of the condition may include the following:

• High levels of ammonia called hyperammonemia
• Poor feeding
• Sleepiness or lack of energy called lethargy
• Vomiting
• Tight, rigid muscles (spasticity)
• Breathing trouble
• Seizures
• Coma

What mutation leads to this?

The condition is caused by a change in the ASL gene. This gene gives your body instructions for making arginosuccinate lyase. This enzyme helps remove the ammonia in your body produced when proteins are broken down.

• Without a working ASL gene, your baby’s body cannot make enough working enzyme.
• As a result, their body cannot properly remove ammonia.
• High levels of ammonia are very dangerous to their body.

How is this condition treated?

It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.

Treatments may include the following:

• Drugs that help remove ammonia from the body
• Diet low in protein
• Arginine supplements to help lower ammonia levels
• Children who receive early and ongoing treatment for argininosuccinic aciduria can have healthy growth and development.

FAQS

Can you help answer any of these frequently asked questions on Argininosuccinate lyase deficiency?

• How common is argininosuccinate lyase deficiency?
• What happens in Argininosuccinase deficiency?
• What is the cause of argininosuccinate lyase deficiency?
• What happens to the fumarate produced by argininosuccinate lyase?
• What causes aciduria?
• Which metabolite would accumulate in patients with a deficiency in arginase?
• What is ASA disease?
• How does arginine remove ammonia?
• How common is urea cycle disorder?
• What is OTC disease?
• How is orotic aciduria treated?
• What is methylmalonic aciduria?
• What is an organic acidemia?
• What causes high arginine levels?
• What is ornithine made from?

Resources

Frequently asked questions

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NIH genetic and rare disease info

• NIH info on Argininosuccinate lyase deficiency

Argininosuccinate lyase deficiency is a rare disease.