Ornithine aminotransferase deficiency

Ornithine aminotransferase (OAT) deficiency is a progressive disorder that affects vision. People affected by OAT experience an ongoing loss of cells in 2 important parts fo the eye - this typically causes nearsightedness, night blindness, and loss of peripheral vision beginning in childhood. Over time, the vision loss gets worse, typically resulting in tunnel vision that eventually leads to blindness by the age of 50.

Symptoms of OAT deficiency can vary, even among members of the same family. Most people have no symptoms other than vision loss. Some newborns with changes at birth can experience other problems related to excess ammonia in the blood that can affect muscle and brain development. Early initiation of a treatment that restricts protein in the diet may slow the progression of symptoms.

Quick facts about ornithine aminotransferase deficiency
Genes: OAT
Inheritance: Autosomal Recessive
Relevant resources for ornithine aminotransferase deficiency

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 ornithine aminotransferase deficiency inherited?

ornithine aminotransferase deficiency 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 ornithine aminotransferase deficiency, 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 ornithine aminotransferase deficiency, 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 ornithine aminotransferase deficiency before or early in pregnancy?

The biggest benefit of screening for ornithine aminotransferase deficiency 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 ornithine aminotransferase deficiency 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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