Citrullinemia type 1

Citrullinemia type 1 is a condition that causes damage to the nervous system due to a build-up of ammonia and other toxic substances in the blood. The severity of the conditions and symptoms experienced can vary between individuals. In the most severe cases, symptoms develop in the first few days of life and can include lack of energy, poor feeding, vomiting, and seizures. Sadly, children with the severe form often die very young. Treatment is focussed on managing symptoms and slowing progression.

There is a less common, milder form of the condition, which develops in late childhood or adulthood. Individuals with the milder form may experience no symptoms, the same symptoms with later onset, or milder symptoms such as low energy, intense headaches, and problems with vision, balance, and coordination.

Quick facts about citrullinemia type 1
Genes: ASS1
Inheritance: Autosomal Recessive
Relevant resources for citrullinemia type 1

A quick genetics rundown

As humans we have about 23,000 genes. These genes are like tiny instruction manuals that influence our health, growth and development. We inherit half of our genes from our biological mum and the other half from our biological dad. These genes are lined up on structures called chromosomes. Most of us have 23 pairs of chromosomes. The first 22 pairs are called autosomes and for the most part - these are the same among men and women. The 23rd pair determine our sex - two X chromosomes for a female and one X and one Y chromosome for males.

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How is citrullinemia type 1 inherited?

citrullinemia type 1 is known as an autosomal recessive condition. For autosomal recessive conditions, if a person has a variation in one copy of their gene, they are a carrier. This means that they are healthy because they also have a working copy of the gene. But, they can still pass their non-working copy to their child.

If the other parent also happens to be a carrier of the same gene, there is a 25% (1 in 4) chance that they both pass this gene variation on to their child — and as such, have a child affected by the disease.

If both parents are carriers of citrullinemia type 1, there’s a one in four chance that their children could develop symptoms.
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What is carrier screening?

Carrier testing is like a checkup for your genes. It tests to see if you carry a gene variation that could cause a serious genetic disease in your child. Eugene offers an inclusive genetic carrier screening panel that includes citrullinemia type 1, but there's a total 301 conditions that can be tested.

Eugene’s carrier test is a clinical grade test that can be done from the comfort of your own home — it’s just a saliva test. You're also paired with a genetic counsellor who provides mindful support and guidance every step of the way.

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Should parents screen for citrullinemia type 1 before or early in pregnancy?

The biggest benefit of screening for citrullinemia type 1 is that it can help future parents understand their reproductive risk so they can be ready and empowered to make more informed decisions. If neither partner are carriers, it provides reassurance and peace of mind that the risk of having a child with a genetic disease is low.

Since 90% of children that have a recessive genetic disease like citrullinemia type 1 had no previous family history of it, it often feels completely out of the blue for the parents. Getting screened is a way to know this risk in advance, which can help familes manage or even prevent the disease in the first place.

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