A Single Genetic Test Can Accurately Diagnose 25 Rare Diseases Faster Than Ever

A quick genetic test can diagnose a large range of rare muscle and nerve diseases with near perfect accuracy.

A family of over 50 inherited diseases, including Huntington's disease and amyotrophic lateral sclerosis, seem to occur when short DNA sequence are repeated too many times.

Many are benign, however, and all living things have them in different patterns and combinations, making them a useful tool for determining relationships between individuals.

Sometimes they arise in problematic parts of our genomes.

Depending on where they occur, long forms of these repeating sequences can cause neurological or neuromuscular damage. There are 37 known genes that are linked to short tandem repeat disorders, so it can take multiple tests before identifying the ones responsible for an individual's symptoms.

It can take over a decade for patients like John to make a decision.

John was eventually diagnosed with CANVAS, a group of diseases. This is a movement disorder that is linked to an expansion of repeat DNA.

A blanket diagnostic test is difficult because there are many ways in which short genes can be repeated.

John says that he had test after test and no answers as to what was wrong.

At the Garvan Institute for Medical Research in Australia, neurologist Kishore Kumar and his colleagues refer to this process as adiagnostic odyssey. John's symptoms get worse as he waits for answers.

While there is no cure for tandem repeat disorders, early diagnosis can help patients manage their symptoms, and hopefully stall some of the disease progression, so the newly developed test should make a big difference to patients.

This new test will completely change how we diagnose these diseases, since we can now test for all the disorders at once with a single DNA test and give a clear genetic diagnosis.

The assessment is based on the use of a technology that can analyze long DNA orRNA fragments in repetitive regions of the human genome.

Researchers can take a single DNA sample from an individual and use changes in electrical current from the interactions between the genes to decode them in real time.

John was one of 37 patients who were tested using this method.

All patients with conditions that were already known were correctly diagnosed.

The current tests require machines as large as fridges, whereas the nanopore technology is no bigger than a stapler. It costs hundreds of thousands of dollars less and could be easily scaled up and distributed.

Researchers are trying to get the method approved. The diagnostic test will be used frequently.

Science Advances published the study.