22q11.2 Deletion: The Most Common Syndrome You Have Never Heard Of

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Danielle Andrew 20 May 2017, 20:38

You wouldn’t be blamed for thinking that 22q11.2 was a postcode or password. My guess is you wouldn’t have thought it was the most prevalent syndrome of its kind. The Conversation

So let’s talk about “22q”.

Everyone has 23 pairs of chromosomes – that’s 46 all together. Chromosomes are made of genes, which themselves are built of DNA. Think of a chromosome as a complete puzzle: the genes are the individual pieces and the DNA is the pattern or picture. When the different pieces are fixed together, they create a complete chromosome. In people with a genetic syndrome like 22q, a piece of the puzzle is missing, leaving the picture incomplete.

In 22q, the missing section is found on the “q arm” of the 22nd chromosome, at a position identified as 11.2 which combined becomes 22q11.2. The missing section can differ in size, meaning people can experience different symptoms. However, there is a core region commonly deleted in all.

The prevalence of 22q is considered to be around one in 2,000 live births globally. This number is constantly under review however, with the syndrome potentially more common than initially thought. Many people go through life without a diagnosis.

What problems occur in 22q?

Because of the myriad problems in 22q, many different specialists are involved in diagnosing and treating it. It doesn’t help that different specialists refer to 22q by different names such as DiGeorge syndrome, or velocardiofacial syndrome. These share a 22q deletion yet are considered different syndromes. In my world of research however, we talk about it as “22q”.

When a diagnosis is first made, the focus is commonly on the physical effects of the syndrome, such as cleft palate and heart defects. These effects are of course dependent on when and why a diagnosis was sought or given. Some diagnoses occur because of behavioural or developmental problems – autism-like symptoms or inattention and hyperactivity, for example – not just physical. These developmental and psychiatric problems come with age but can be traced back to earlier years.

22q has one of the highest prevalences of developmental delay and congenital heart disease, second only to Down’s syndrome. Further similarities include both having a broad range of symptoms – including poor muscle tone and differences in digit length, both fingers and toes – and facial features. These tend to be more stereotyped in Down’s syndrome, but can be evident in 22q.

A child with 22q11.2 deletion syndrome. Prof Victor Grech/Wikimedia, CC BY-SA

22q also puts individuals at increased risk of schizophrenia. In the general population, 1-2% of people have schizophrenia. In 22q, this rate is higher, at around 25-30% of people. 22q is one of the highest implicated genetic changes of its kind for development of schizophrenia. Strikingly, this elevated risk is higher than having one parent with schizophrenia, which is 10%. Having such a pronounced and stigmatised disorder at this risk level highlights the need for more understanding of 22q, as well as better interventions and treatments.

Other psychiatric disorders are more prevalent in 22q as well, including anxiety disorders, attention-deficit hyperactivity disorder (ADHD) and autism. Epilepsy and impaired motor coordination are also common.

One of the most uncharted problems of 22q is that of sleep disturbances, which is what I am currently researching. Some people with 22q have physical sleep-related problems such as obstructive sleep apnoea, however sleep-related behavioural and psychological problems have yet to be fully investigated.

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