Leber congenital amaurosis 8/CRB1-related disorders

CRB1-related disorders are a group of eye disorders that can cause progressive vision loss. This is because the CRB1 gene provides instructions for making a protein that plays an important role in normal vision. This protein is found in the brain and the retina, which is the tissue at the back of the eye that detects light and colour.

The severity, progression and age at which symptoms appear for these conditions vary from person to person and even within families. Some people experience loss of night vision in their childhood or teen years, and their vision continues to worsen over years or decades until they are legally blind. This condition is known as retinitis pigmentosa (RP). Other people show severe visual impairment beginning in infancy, a condition known as Leber congenital amaurosis (LCA).

Quick facts about Leber congenital amaurosis 8/CRB1-related disorders
Genes: CRB1
Inheritance: Autosomal Recessive
Relevant resources for Leber congenital amaurosis 8/CRB1-related disorders

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 Leber congenital amaurosis 8/CRB1-related disorders inherited?

Leber congenital amaurosis 8/CRB1-related disorders 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 Leber congenital amaurosis 8/CRB1-related disorders, 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 Leber congenital amaurosis 8/CRB1-related disorders, 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 Leber congenital amaurosis 8/CRB1-related disorders before or early in pregnancy?

The biggest benefit of screening for Leber congenital amaurosis 8/CRB1-related disorders 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 Leber congenital amaurosis 8/CRB1-related disorders 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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