It took 19 fruitless years before Rebecca Clough finally had a name for what was wrong with her.

The South Auckland woman was born with partial paralysis of her facial muscles, making the simple acts of drinking, eating and even smiling almost impossible.

Despite a barrage of tests, doctors remained baffled.

Her voice wavered as she recalled her childhood: "It was tough."

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It was only when her brother Arthur was born in four years ago, with all the same crippling symptoms, that doctors realised that the cause was genetic.

By then, remarkable strides in DNA science had been made.

It encouraged a group of New Zealand geneticists to take another look at patients with mystery conditions.

They began to study 40 people from 12 families - including the Clough siblings - seeking long-awaited answers.

Previously, scientists relied on painstaking guesswork to try to pinpoint the one gene in around 21,000 that was causing a disease.

Professor Stephen Robertson, from Otago University, said it was "like being stuck in the slow lane".

Rebecca Clough was born with partial paralysis of her facial muscles, making the simple acts of drinking, eating and even smiling almost impossible.
Rebecca Clough was born with partial paralysis of her facial muscles, making the simple acts of drinking, eating and even smiling almost impossible.

"When you sequenced a single gene it would be several thousand DNA letters long. You'd look at those letters one by one."

Now, using new technology called Next Generation Sequencing, scientists could simply take DNA and run it through a machine, decoding a person's entire genetic code at once.

It meant they could now spot most anomalies.

"The trouble is we all have variations throughout our genome, that probably don't cause disease," Robertson said.

"Telling the difference between those variants and the ones that might cause something more catastrophic is the challenge."

It took a lot of molecular sleuthing through Rebecca and Arthur's DNA before Robertson and his team whooped at the "eureka moment".

Professor Stephen Robertson, from Otago University, has helped reveal a rare condition afflicting people around the world. Photo / Supplied
Professor Stephen Robertson, from Otago University, has helped reveal a rare condition afflicting people around the world. Photo / Supplied

They found variants within a gene involved in muscle cell development, and realised it had been studied before in mice, producing similar muscular paralysis.

They sent their finding overseas, where scientists exploring the same gene confirmed the diagnosis.

Finally, they had a name for Rebecca and Arthur's condition: Carey-Fineman-Ziter syndrome.

The muscle disorder was so rare, only 10 people worldwide had been diagnosed with it.

But Clough said that even though she has a one-in-a-billion condition, it meant everything to know they were not alone.

"It was kind of amazing. There's other people with this around the world. I was shocked."

It meant her family had been able to contact a man in the United States who has had the condition for 39 years, easing their fears about how her health could deteriorate over time.

Mum Sarah with Rebecca's brother Arthur who was born four years ago with all the same crippling symptoms.
Mum Sarah with Rebecca's brother Arthur who was born four years ago with all the same crippling symptoms.

"It's kind of impressive to find out what I've got, what I can cope with and what I can't," she said.

"I can live a normal life. Do what normal people do."

Robertson said that although there is no cure, being able to give Clough an answer was hugely rewarding.

"This idea that actually a genetic discovery can take that alone feeling away is actually one of the most positive things that we as geneticists can feel," he said.

"Sure we can't fix anybody. We can't rewire things or fix someone's genetic code … but understanding what it is puts it in its place."

Through the cutting-edge research, scientists were also able to give five other people in the study a diagnosis.

Co-author Professor Cristin Print, from the University of Auckland said he was delighted.

"For half of the families in the study this has given them some certainty about what the gene change is that is responsible for their condition," Print said.

"That has allowed them to do some planning for the future, and understand what is going on."

Unfortunately there were others waiting for that same certainty.

Research showed half the patients who visit genetics clinics in New Zealand remained undiagnosed.

Print was hoping this type of genomic technology becomes commonplace, so no one else had to wait as long as Clough for an answer.

- Aotearoa Science Agency