Adenosine deaminase deficiency

Adenosine deaminase (ADA) deficiency is a metabolic disorder that primarily affects the development and function of a person's white blood cells. White blood cells form a crititical component of the immune system and people with ADA deficiency develop a condition called severe combined immunodeficiency (SCID) or combined immunodeficiency (CID).

People with SCID lack virtually all immune protection from bacteria, viruses, and fungi. They are prone to repeated and persistent infections that can be very serious or life-threatening. These infections are often caused by "opportunistic" organisms that ordinarily do not cause illness in people with a normal immune system. The main symptoms of SCID are pneumonia, chronic diarrhea, and widespread skin rashes. Most individuals with SCID due to ADA deficiency are diagnosed with SCID in the first 6 months of life. Without treatment, these babies usually do not survive past age 2.

In about 10 percent to 15 percent of cases, onset of immune deficiency is delayed to between 6 and 24 months of age (delayed onset) or even until adulthood (late onset) and is called CID. Immune deficiency in later-onset CID is usually less severe but over time, people with CID due to ADA deficiency may develop chronic lung damage, malnutrition, and other health problems.

Quick facts about adenosine deaminase deficiency
Genes: ADA
Inheritance: Autosomal Recessive
Relevant resources for adenosine deaminase 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 adenosine deaminase deficiency inherited?

adenosine deaminase 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 adenosine deaminase 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 adenosine deaminase 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 adenosine deaminase deficiency before or early in pregnancy?

The biggest benefit of screening for adenosine deaminase 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 adenosine deaminase 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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