Aicardi-Goutieres syndrome (SAMHD1-related)

Aicardi-Goutières syndrome (AGS) is a condition that mainly affects the brain, skin, and immune system. It is sadly a progressive life-limiting neurological condition.

Most babies appear healthy at birth, but about 20% are born with an enlarged liver and spleen (hepatosplenomegaly), elevated blood levels of liver enzymes, low numbers of platelets in the blood (thrombocytopenia), and neurological abnormalities. Babies affected by AGS due to variations in the SAMHD1 gene usually experience episodes of severe brain dysfunction within the first year of life that may last several months. During this time, babies also experience inflammation and tissue damage in the central nervous system, which causes permanent neurological damage including loss of white matter (leukodystrophy) and abnormal deposits of calcium (calcification) in the brain. This brain damage typically leads to profound intellectual disability. Other symptoms include effects on the function of large muscle groups, weak muscle tone, blood abnormalities and problems with autoimmune function. Symptoms can vary between individuals.

Because of the severe health problems associated with AGS, most patients sadly do not survive past childhood. There is also a less common, milder, later onset form of AGS. Treatment is focused on managing the symptoms present in each individual.

Quick facts about Aicardi-Goutieres syndrome (SAMHD1-related)
Genes: SAMHD1
Inheritance: Autosomal Recessive
Relevant resources for Aicardi-Goutieres syndrome (SAMHD1-related)

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 Aicardi-Goutieres syndrome (SAMHD1-related) inherited?

Aicardi-Goutieres syndrome (SAMHD1-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 disease.

If both parents are carriers of Aicardi-Goutieres syndrome (SAMHD1-related), 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 Aicardi-Goutieres syndrome (SAMHD1-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.

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Should parents screen for Aicardi-Goutieres syndrome (SAMHD1-related) before or early in pregnancy?

The biggest benefit of screening for Aicardi-Goutieres syndrome (SAMHD1-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 disease is low.

Since 90% of children that have a recessive genetic disease like Aicardi-Goutieres syndrome (SAMHD1-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 disease in the first place.

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