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Major study sheds light on rare genetic diseases affecting 5,500 children

Thousands of children have been diagnosed thanks to the study
Thousands of children have been diagnosed thanks to the study Copyright Canva
Copyright Canva
By Luke Hurst
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The findings mean many more families could now get answers faster about their children’s conditions.


Thousands of children have been diagnosed with rare developmental disorders in a major genetic sequencing study in the UK.

More than 13,500 families across the UK and Ireland were recruited for the study, all of which had children with an undiagnosed severe developmental disorder.

Through genetic sequencing of the children and their parents’ genes, combined with other high-tech methods, genetic diagnoses for around 5,500 children have now been made.

The methods used in the nationwide study could help to improve diagnosis for such conditions across the world - something which lead study author Caroline Wright, Professor of Genomic Medicine at the University of Exeter, said was “absolutely critical for families with rare conditions”.

Such conditions affect around one in 17 people, and most are genetic, meaning they can be diagnosed using the same genomic sequencing technology, she added.

“The families in our study were desperate for answers, which can make a huge difference to clinical management and quality of life. By sharing our findings, many more families in the future should get answers faster,” she said.

The Deciphering Developmental Disorders (DDD) study is a collaboration between the NHS and the Wellcome Sanger Institute in the UK. The results of the study were published in the New England Journal of Medicine.

60 new conditions uncovered

The diagnoses in the study were in more than 800 different genes, and they included 60 new conditions that were discovered by the study.

While the parents of the children had their genes sequences in the search for answers, the study found around three quarters of the conditions were caused by spontaneous mutations that were not inherited.

The researchers said many of the diagnoses were possible only because data was combined from across diagnostic centres in the UK and Ireland.

The chances of success in getting a diagnosis were lower in families of non-European ancestry, the team said, calling for increased research participation for under-represented groups.

“Undiagnosed patients with rare genetic diseases have the most to lose if they are not given an opportunity to participate in research and if their data are kept in silos,” said senior co-author Matthew Hurles, incoming Director of the Wellcome Sanger Institute and Honorary Professor of Human Genetics and Genomics at the University of Cambridge.

“As these genomic technologies move into routine healthcare, ensuring that undiagnosed patients can still benefit from research on their data will remain incredibly important”.

Information on the conditions identified in the study will be fed into tests applied by other similar diagnostic services used in the NHS, such as the Rapid Genome Sequencing Service for acutely unwell children with a likely monogenic disorder, which can provide a genetic diagnosis for babies and children in or facing critical care within just 10 days.

Feeling less lonely

Getting the right diagnosis is important not only for guiding clinical care, but it can also bring together families in support networks to reduce the isolation of having a child with a rare developmental condition.

One condition discovered by the study is called Turnpenny-Fry syndrome, which is caused by extremely rare changes in a gene called PCGF2. The disorder causes learning difficulties, impaired growth, and distinctive facial features that include a large forehead and sparse hair.

Jessica Fisher’s son Mungo was diagnosed with the condition, and she initially felt the diagnosis had come too late, as he was already 18.

She had already lived through years of uncertainty, not knowing how his condition would develop. But with the diagnosis, she was connected to another family diagnosed through the study, and a Facebook support group was set up.


There are now around 36 families across the world in the group - an invaluable community for those who are newly diagnosed.

“When I first saw a picture emailed to me of the other family’s child it was really emotional,” Fisher said in a statement.

“We’d always looked around for children who might look like Mungo – and here was a child in Australia who could have been his sibling. For a few months it was just us two families, but then it slowly started to grow. We now have families from countries including America, Brazil, Croatia, Indonesia”.

Being a part of such a group reduced the feeling of isolation, she added.

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