Single test can detect more than 50 genetic diseases

Dr Ira Deveson, Head of Genomics Technology at Garvan said: ‘We correctly diagnosed all the patients with known diseases, including Huntington’s disease, fragile X syndrome, ataxia ataxia. hereditary cerebellar, muscular dystrophy, myoclonic epilepsy, motor neurone disease and more. Institute and senior author of the study.

The diseases covered in the test belong to a group of more than 50 diseases caused by abnormally long repetitive DNA sequences in a person’s genes – known as ‘short repeat extension (STR) disorders’.

“They are often difficult to diagnose due to the complex symptoms that patients experience, the challenging nature of these repetitive sequences, and the limitations of currently available genetic testing methods,” said Dr.

Research published today in the journal Science Advances shows the test is accurate and allows the team to begin validation to make this test available in pathology services worldwide.

One patient in the study, John, first realized something was wrong when he had unusual problems keeping his balance during a skiing lesson.

‘It is worrying that the symptoms, over the years, have increased in severity; from active and mobile to unable to walk without support. John, who was eventually diagnosed with a rare genetic disease called CANVAS, which affects the brain.

He said: “It is reassuring to finally have my diagnosis confirmed genetically and it is exciting to know that in the near future, people with these types of conditions will be able to be diagnosed. faster than me”.

Dr Kishore Kumar, co-author of the study and a clinical neurologist at Concord Hospital, said: “For patients like John, the new test will be a game changer, helping to end what ever can often be a taxing diagnostic adventure.”

Repetitive dilation disorder can run in families, can be life-threatening, and is often associated with muscle and nerve damage, as well as other complications throughout the body.

Faster, more accurate diagnosis for patients avoiding ‘diagnostic adventures’

Dr Kumar said current genetic testing for dilation disorders can be ‘hit and miss’. ‘When a patient has symptoms, it’s difficult to know which of these more than 50 genetic conditions they may have, so their doctor must decide which gene to test based on symptoms and family history. that person’s family. If that test is negative, the patient will not have an answer. This test can go on for years without finding the genes associated with their disease. We call this ‘diagnostic adventure’, and it can be quite stressful for patients and their families,’ he said.

‘This new test will completely revolutionize the way we diagnose these diseases, as we can now test for all disorders at once with a single DNA test and make a diagnosis. genetic predisposition, helping patients avoid years of unnecessary muscle or nerve biopsies for diseases they don’t have. Dr Kumar said: ‘No, or risky treatments suppressed their immune systems.

Although dilated dilatation disorder cannot be cured, a quicker diagnosis can help doctors identify and treat its complications earlier, such as heart problems associated with ataxia. the Friedreich Peace.

Scan for known and new diseases

Using a single sample of DNA, usually extracted from blood, the test works by scanning a patient’s genome using a technology called Nanopore sequencing.

“We programmed the Nanopore device to collect about 40 genes known to be involved in these disorders and read through the long, repetitive DNA sequences that cause disease,” he said. ‘By unraveling the two DNA sequences and reading the repeated letter sequences (combining A, T, G or C), we were able to scan for unusually long repeats in the patient’s genes, which are signs of illness.’

Dr Deveson said: “In one test, we were able to search for every known disease-causing repeat extension and potentially uncover new sequences potentially associated with undescribed diseases. ,” said Dr. Deveson.

Upgrade for wider use in the next five years

The Nanopore technology used in this test is smaller and cheaper than standard tests, which the team hopes will make it easier to get into pathology laboratories. Dr Deveson said: “With Nanopore, the sequencing device has been reduced from the size of a refrigerator to the size of a stapler and costs about $1000, compared with the hundreds of thousands needed. essential for mainstream DNA sequencing technologies”.

The team hopes to see their new technology used in diagnostic practice within the next two to five years. One of the key steps towards that goal is obtaining appropriate clinical certification for the method.

Dr Gina Ravenscroft, co-author of the study and a researcher working in rare disease genetics at the Harry Perkins Institute for Medical Research, said that once approved, the trial will also translate research into diseases. genetic.

She said: ‘Adult-onset genetic disorders do not receive as much research attention as those that appear in early life. ‘By finding more people with these rare adult diseases, and who may already have symptoms, we will be able to learn more about a variety of rare diseases through cohort studies. , which is very difficult to do.’

Source: Eurekalert

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