Children and Youth with Special Health Needs (CYSHN)
Argininosuccinate Acidemia (ASA)
On this page...
- What is ASA?
- What causes ASA?
- What causes the ASAL enzyme to be absent or not working correctly?
- How is ASA deficiency inherited?
- Is genetic testing available?
- What other testing is available?
- Can you test during pregnancy?
- Can other members of the family have ASA or be carriers?
- Can other family members be tested?
- How many people have ASA?
- Does ASA happen more often in a certain ethnic group?
- Does ASA go by any other names?
- What is the treatment for ASA?
- What happens when ASA is treated?
- If ASA is not treated, what problems occur?
This fact sheet has general information about ASA. Every child is different and some of these facts may not apply to your child specifically. Certain treatments may be recommended for some children but not others. Children with ASA should be followed by a metabolic doctor in addition to their primary doctor.
What is ASA?
ASA stands for “argininosuccinate acidemia”. ASA is one type of amino acid disorders. People with this condition cannot remove ammonia from the body. Ammonia is a harmful substance. It is made when protein and its building blocks, amino acids, are broken down for use by the body.
|Amino Acid Disorder:
Amino acid disorders (AAs) are a group of rare inherited conditions. They are caused by enzymes that do not work properly.
Protein is made up of smaller building blocks called amino acids. A number of different enzymes are needed to process these amino acids for use by the body. Because of missing or non-working enzymes, people with amino acid disorders cannot process certain amino acids. These amino acids, along with other toxic substances, then build up in the body and cause problems.
The symptoms and treatment vary between different amino acid disorders. They can also vary from person to person with the same amino acid disorder. See the fact sheets for each specific amino acid disorder.
Amino acid disorders are inherited in an autosomal recessive manner and affect both males and females.
What causes ASA?
ASA is one of a small number of conditions called “urea cycle disorders” (UCD).
It occurs when an enzyme called “argininosuccinic acid lyase” (ASAL), is either missing or not working properly. This enzyme’s job is to help remove ammonia from the body.
When the ASAL enzyme is not working, ammonia and other harmful substances build up in the blood and cause brain damage. If not treated, excess ammonia can cause death.
What causes the ASA enzyme to be absent or not working correctly?
Genes tell the body to make various enzymes. People with ASA have a pair of genes that do not work correctly. Because of the changes in this pair of genes, the ASAL enzyme either does not work properly or is not made at all.
How is ASA inherited?
ASA is inherited in an autosomal recessive manner. It affects both boys and girls equally.
Everyone has a pair of genes that make the ASAL enzyme. In children with ASA, neither of these genes works correctly. These children inherit one non-working gene for the condition from each parent.
Parents of children with ASA rarely have the disorder. Instead, each parent has a single non-working gene for ASA. They are called carriers. Carriers do not have the condition because the other gene of this pair is working correctly.
When both parents are carriers, there is a 25% chance in each pregnancy for the child to have ASA. There is a 50% chance for the child to be a carrier, just like the parents. And, there is a 25% chance for the child to have two working genes.
Genetic counseling is available to families who have children with ASA. Genetic counselors can answer your questions about how the condition is inherited, choices during future pregnancies, and how to test other family members. Ask your doctor about a referral to a genetic counselor.
Is genetic testing available?
Genetic testing for ASA is available. Genetic testing, also called DNA testing, looks for changes in the pair of genes that cause the condition. Ask your metabolic doctor or genetic counselor whether DNA testing is available to your family.
DNA testing is not necessary to diagnose your child. However, it can be helpful for carrier testing or prenatal diagnosis, discussed below.
What other testing is available?
Special tests on blood, urine or skin samples can be done to confirm ASA. Talk to your metabolic doctor if you have questions about this type of testing.
Can you test during pregnancy?
If both gene changes have been found in the child with ASA, DNA testing can be done during future pregnancies. The sample needed for this test is obtained by either CVS or amniocentesis. CVS stands for Chorionic Villus Sampling, which is a special test done early in pregnancy. During CVS, a small sample of the placenta is removed for genetic testing.
If DNA testing would not be helpful, an enzyme test can be done on cells from the fetus. Again, the sample needed for this test is obtained by either CVS or amniocentesis.
Parents may choose to have testing during pregnancy or wait until birth to have the baby tested. A genetic counselor can talk to you about your choices and answer questions about prenatal testing or testing your baby after birth.
The brothers and sisters of a baby with ASA have a small chance of being affected even if they haven't had symptoms. Finding out whether other children in the family have this condition may be important because early treatment may prevent serious health problems. Ask your metabolic doctor whether your other children should be tested.
Brothers and sisters who do not have ASA still have a chance to be carriers like their parents. Except in special cases, carrier testing should only be done in people over 18 years of age.
Each of the parents' brothers and sisters has a 50% chance to be a carrier. It is important for other family members to be told that they could be carriers. There is a small chance they are also at risk to have children with ASA.
When both parents are carriers, newborn screening results are not sufficient to rule out the condition in a newborn baby. In this case, special diagnostic testing should be done in addition to newborn screening.
Brothers and sisters of a child with ASA can be tested using blood, urine, or skin samples.
If both gene changes have been found in your child, other family members can have DNA testing to see if they are carriers.
If the gene changes cannot be found, DNA testing would not be helpful for carrier testing. However, other methods of carrier testing may be available. Your metabolic doctor or genetic counselor can answer your questions about carrier testing.
How many people have ASA?
This is a rare condition. About one in every 70,000 babies in the United States is born with ASA.
Does ASA happen more frequently in a certain ethnic group?
ASA does not happen more often in any specific race, ethnic group, geographical area or country.
Does ASA go by any other names?
ASA is sometimes also called:
- Argininosuccinase deficiency
- Argininosuccinic aciduria
- Argininosuccinic acidemia
- Argininosuccinic acid lyase deficiency
- Argininosuccinyl-CoA lyase deficiency
- ASL deficiency
- Arginine succinate lyase deficiency
What is the treatment for ASA?
Your baby's primary doctor may work with a metabolic doctor and a dietician to care for your child.
Prompt treatment is needed to prevent the build-up of ammonia. You should start treatment as soon as you know your child has this condition.
Low-protein diet and/or special medical foods and formula
Eating foods high in protein can cause ammonia to build up in the blood, resulting in severe illness. Many vegetables and fruits have only small amounts of protein and can be eaten in carefully measured amounts.
Do not remove all protein from the diet. Your child still needs a certain amount of protein for normal growth and development. Your dietician will help you create the best food plan for your child.
Medical foods and formula
Your baby may be given a special formula that contains the correct amount of nutrients and amino acids. Your metabolic doctor and dietician will decide whether your child needs this formula.
Your child’s exact food plan will depend on many things such as his or her age, weight, and general health. Your dietician will fine-tune your child’s diet over time. Any diet changes should be made under the guidance of a dietician familiar with ASA.
There are other medications that can help prevent high ammonia levels. These can either be taken by mouth or by tube feedings. Your metabolic doctor will decide whether your child needs this type of medication.
During episodes of high blood ammonia, children need to be treated in the hospital. Medications to remove ammonia are often given by IV. Sometimes dialysis is needed to remove ammonia from the blood.
Your child will have regular blood tests to measure amino acid and ammonia levels. Your child’s diet and medication may need to be adjusted based on blood test results.
Call your doctor at the start of any illness:
Symptoms of high ammonia often need to be treated in the hospital. Ask your metabolic doctor if you should carry a special travel letter with medical instructions for your child’s care.
What happens when ASA is treated?
With prompt and lifelong treatment, children with ASA may be able to live healthy lives with typical growth and learning. Early treatment can help prevent high ammonia levels. This lessens the risk for brain damage and mental retardation.
Even with treatment, some children still have episodes of high ammonia. This can result in brain damage and can cause lifelong learning problems, mental retardation, or spasticity.
If ASA is not treated, what problems occur?
Normally, the body changes ammonia into a substance called “urea”. Urea is then safely removed in the urine. If ammonia is not changed to urea, it begins to build up in the blood and can be very harmful. If ammonia levels remain high for too long, severe brain damage can occur.
The symptoms and the age they start vary from person to person. There are two main forms of ASA. In the most common form, the symptoms start shortly after birth. There is also a milder form in which symptoms start in late infancy or early childhood.
ASA in newborns
Infants are healthy at birth but quickly develop symptoms. Within a few days of life, babies have high levels of ammonia in their blood. Some of the first symptoms of high blood ammonia are:
- poor appetite
- excess sleepiness or lack of energy
If not treated, high ammonia levels can cause:
- muscle weakness
- decreased or increased muscle tone
- breathing problems
- problems staying warm
- swelling of the brain
- coma, and sometimes death
Other effects of ASA deficiency can include:
- poor growth
- enlarged liver
- delays in learning or mental retardation
Without treatment, many babies die within the first few weeks of life.
ASA deficiency in childhood
In this milder form, symptoms start later in infancy or childhood. Some common symptoms in children who are not treated are:
- poor growth
- dry, brittle hair
- behavior problems
- learning disabilities or mental retardation
- avoidance of meat and other high protein foods
- enlarged liver
- small head size
- episodes of excess ammonia in the blood
Episodes of high blood ammonia often happen:
- after long periods of going without food
- during illness or infection
- after high-protein meals
In children, some of the first symptoms of high blood ammonia are:
- poor appetite
- intense headache
- extreme sleepiness or lack of energy
- slurred speech
- poor coordination and balance problems
If not treated, children with high blood ammonia levels can develop:
- breathing problems
- swelling of the brain
- coma, sometimes leading to death
Some people have very mild symptoms and are only found to be affected after a brother or sister is diagnosed.
Where can I find more information?
Medically Prescribed Formula: a table that provides a list of commonly prescribed medical foods and formulas and /or medication for this disorder.
National Library of Medicine Genetics Home Reference: Argininosuccinic Aciduria http://ghr.nlm.nih.gov/condition/argininosuccinic-aciduria
National Urea Cycle Disorders Foundation
CLIMB (Children Living with Inherited Metabolic Diseases)
For additional genetics information and resources:
- Genetic Alliance
- Region 4 Genetics Collaborative
- Partnering with your Doctor The Medical Home Approach: A guide for families with children who have genetic conditions - The Guide is intended to be a user-friendly, hands-on tool to support families of children who have genetic conditions to move forward in obtaining and providing a medical home for their children. The guide provides definitions, examples and tools for families to use when working with the doctor to develop a medical home.
More help available from Children and Youth with Special Health Needs (CYSHN):
- Resources: Financial and Other
- Early Childhood Intervention
- Resources for Children and Families
- Youth and Young Adults - Planning for the Future
- Emergency Planning
- Medical Home
We would like to acknowledge the Star G Project. The information on the fact sheet was obtained from the Star G Project. For the most up-to-date information on the disorder please visit their web site at http://www.newbornscreening.info. Each fact sheet was extensively reviewed by family support groups, metabolic specialists across the country and the Star G steering committee.
THIS INFORMATION DOES NOT PROVIDE MEDICAL ADVICE. All content, including text, graphics, images and information are for general informational purposes only. You are encouraged to confer with your doctor or other health care professional with regard to information contained on this information sheet. After reading this information sheet, you are encouraged to review the information carefully with your doctor or other healthcare provider. The Content is not intended to be a substitute for professional medical advice, diagnosis or treatment. NEVER DISREGARD PROFESSIONAL MEDICAL ADVICE, OR DELAY IN SEEKING IT, BECAUSE OF SOMETHING YOU HAVE READ ON THIS INFORMATION SHEET.
|Updated Tuesday, 04-Sep-2012 11:03:53 CDT|