Zellweger spectrum disorder (ZSD) is a group of conditions that cause individuals to produce either a reduced amount of functional peroxisomes or no functional peroxisomes at all. Peroxisomes help break down and manage toxic substances inside a person's cells. If the peroxisomes are not working, and cannot break down the toxic substances, they will build up in the cell causing damage to the cell.
Genetic changes in at least twelve genes cause ZSD and can cause varying severity of the condition. Individuals with the most severe form of ZSD have Zellweger syndrome and typically present early in infancy with symptoms such as poor muscle tone (hypotonia), distinctive facial features, feeding problems, hearing and vision loss, and seizures. Individuals with neonatal adrenoleukodystrophy (NALD) or infantile Refsum disease have various symptoms that are less severe and that do not develop until late infancy or early childhood.
Individuals with Zellweger syndrome sadly do not survive past the first year of life. Individuals with NALD survive into childhood, and those with infantile Refsum disease may survive to adulthood. Treatment for ZSD is focused on management of the symptoms.
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.
Zellweger spectrum disorder (PEX12-related) 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 condition.
If both parents are carriers of Zellweger spectrum disorder (PEX12-related), there's a one in four chance that their children could develop symptoms.
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 condition in your child. Eugene offers an inclusive genetic carrier screening panel that includes Zellweger spectrum disorder (PEX12-related), 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.Learn more about carrier screening
The biggest benefit of screening for Zellweger spectrum disorder (PEX12-related) 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 condition is low.
Since 90% of children that have a recessive genetic condition like Zellweger spectrum disorder (PEX12-related) 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 condition in the first place.