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Mitochondrial complex IV deficiency

Mitochondrial complex IV deficiency is a group of conditions with several subtypes that affects movement and mental ability. One of these subtypes is called Leigh syndrome; French Canadian type (LSFC).

Individuals affected by LSFC have distinctive facial features and experience delayed developmental milestones such as growth, crawling and walking, and talking, due to progressive muscle weakness and deterioration of the brain. They can also experience episodes of sudden onset of illness which can be life threatening.

Sadly, most children affected by LSFC do not live beyond infancy. In rare cases, they may experience milder symptoms and live into childhood or adulthood.

Quick facts about mitochondrial complex IV deficiency
Inheritance: Autosomal Recessive
Alternative Names: Cox deficiency, French Canadian type, Leigh syndrome, Saguenay Lac saint Jean type, Cox deficiency, Saguenay Lac saint Jean type, Cytochrome c oxidase deficiency, French Canadian type, Leigh syndrome, Leigh syndrome, French Canadian type
Relevant resources for mitochondrial complex IV 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 mitochondrial complex IV deficiency inherited?

mitochondrial complex IV 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 condition.

If both parents are carriers of mitochondrial complex IV deficiency, there's a one in four chance that their children could develop symptoms.

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 condition in your child. Eugene offers an inclusive genetic carrier screening panel that includes mitochondrial complex IV 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 mitochondrial complex IV deficiency before or early in pregnancy?

The biggest benefit of screening for mitochondrial complex IV 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 condition is low.

Since 90% of children that have a recessive genetic condition like mitochondrial complex IV 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 condition in the first place.