Argininosuccinic Aciduria

Argininosuccinate lyase deficiency


Type of disease: Rare conditions

Argininosuccinic aciduria (ASA) is a rare genetic condition resulting from a mutation (error) in a person’s DNA. People with ASA have too much ammonia in their blood. ASA is considered a urea cycle disorder. The protein we get from food is broken down into its amino acids or building blocks. We typically eat more protein than needed; therefore we often have more amino acids than we need. Enzymes (special proteins) break down the extra amino acids and one of the waste products is nitrogen. This nitrogen is normally changed by 6 enzymes in the urea cycle to urea which we get rid of in our urine. If the cycle is not complete, ammonia, one of the products made in the urea cycle builds up. In this case the enzyme, arginosuccinic acid lyase (ASAL), is not working and this causes high levels of ammonia to be in the blood.

Changes in the ASL gene cause ASA and it is an autosomal recessive condition. There are two forms of ASA. Symptoms of the most common form usually show in the first few days of life. In the second form, signs may begin to show during late infancy or early childhood. Symptoms of ASA include poor appetite, irritability, vomiting, tiredness, seizures, trouble breathing, uncontrolled body movements, or delayed growth. Treatment may include a specific diet in order to avoid certain proteins that cannot be broken down. Special foods or formulas may also be recommended. Early diagnosis has shown to be effective in improving the health of individuals with HMG. Many babies are screened at birth so that treatment may begin early, however the conditions included in newborn screening vary state by state. For more information, visit Baby’s First Test. Talk with your doctor about the most current treatments. Support groups also are a good source of information. A genetic counselor will help you understand the genetics.

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