Children with rare diseases in England are among the first in the world to be receiving a form of pioneering DNA testing which could more than double the chances of diagnoses - thanks to scientists at the University of Exeter.

In just a single test, whole exome sequencing looks for thousands of rare conditions by identifying genetic mutations in a patient's DNA.

It can improve and speed up diagnoses of children with rare diseases, of which there are between 6,000 and 8,000 known ones.

80% of these have a genetic factor.

NHS England hopes up to 700 children will benefit from the tests each year.

Since they were first rolled out on the NHS on 1 October 2019, 80 babies and children have been tested - just under half have received diagnoses.

It's being offered to children in neonatal or paediatric intensive care units when it's suspected they have a genetic condition.


The test, delivered by the South West Genomic Laboratory Hub, costs around £2,000 and has the potential to more than double the chance of a successful diagnosis.

Scientists from the University of Exeter are behind the development of the test. Credit: PA images

How does it work?

  • It looks for mutations in pieces of an individual's DNA that provide instructions for making proteins, usually taken from a blood sample.

  • The majority of disease-causing variants are thought to lie within these regions, known collectively as the exome.

  • The technique is faster than standard genetic tests.

The new testing can also show which patients are unlikely to respond to certain treatments.

This could prevent children from having to take unnecessary medication and experience the potential side effects.


Standard tests usually result in a successful diagnosis 20% of the time.


Just under half of those who underwent the whole exome sequencing received a successful diagnosis.

Henry Dunn from Exeter had the new test at 20 months old after he experienced a range of undiagnosed problems and a spell in hospital after he was born.

Within a week of having the pioneering treatment he was diagnosed with a rare disease - Costello syndrome - than can affect several organ systems and lead to an increased risk of childhood cancer.

He was closely monitored and after developing cancer twice, it was detected early enough and successfully treated on both occasions.

Henry is now in remission. His mother, Lauren Dunn, said that without the exome sequencing, her son's diagnoses and treatment "would likely have been delayed."

Knowing that Henry has Costello syndrome provided the missing piece of the puzzle and means that he receives the medical management that he needs to make sure his needs are met and to help him achieve his full potential.

Lauren Dunn, Henry's mum
So far 80 babies and children have undergone the new testing process. Credit: PA images

NHS England has high hopes for its future.

Once again the NHS is at the forefront of the genomic revolution with patients in England the first to be routinely offered this cutting edge treatment as part of the Long Term Plan. This quick and accurate new test means rapid diagnosis and reassurance for families when they need it most and give babies and children the best chance of a healthy and happy life. In the last year alone, scores of patients have received game-changing new treatments such as CAR-T therapy and targeted radiotherapy at the NHS's new £125 million Proton Beam centre. Over the next decade the NHS will continue to expand the range of personalised, precision medicines, including rolling out genomic testing to all people with rare diseases and patients with cancer.

Sir Simon Stevens, NHS England chief executive

Heath Secretary Matt Hancock is also optimistic.

The pain for families seeking a diagnosis for their sick children is unimaginable. These cutting-edge DNA tests will much more rapidly diagnose rare diseases, helping to put an end to uncertainty and allowing children to receive the best possible treatment.

Health Secretary, Matt Hancock