Argininosuccinic aciduria (ASA)

What happens in this disease?

When the body uses protein, it makes a waste product called nitrogen. The liver turns this waste into urea and removes it in the urine. In this disease, an enzyme needed for this job is missing. Nitrogen builds up in the blood as ammonia. When there is too much ammonia, it harms the brain most of all.

Which symptoms can occur?

The severe form often begins in the first days after birth. The mild form may appear later and come in attacks.

• In a baby: poor feeding, vomiting and unusual sleepiness
• Fast breathing and seizures (fits)
• A large liver and, over time, liver damage
• Dry, brittle hair that breaks easily
• Developmental delay and learning difficulties
• High blood pressure (sometimes)
• Ammonia attacks during illness or stress

How is it diagnosed?

The levels of ammonia and amino acids in the blood are measured. Argininosuccinic acid is found to be high in the blood or urine. The diagnosis can be confirmed with a genetic test. In some countries, it is found through newborn screening.

Treatment and care

Care is led by a metabolic team. The main approach is a special diet that limits protein. Extra amino acid supplements and treatments that help remove nitrogen are used. If ammonia rises very high, hospital treatment is needed; sometimes blood dialysis is done. A liver transplant may be considered for some people. The blood, liver and blood pressure are checked regularly. Physiotherapy and speech therapy support development. The doctor who follows the disease decides which treatment is suitable.

For the family: inheritance and genetic counselling

The disease is passed on through recessive inheritance. The mother and father are usually healthy carriers. For a couple who are both carriers, the chance of having an affected child is 1 in 4 in each pregnancy. In marriages between relatives, the chance of carrying the same gene is higher. Genetic counselling is recommended for the family.