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TORONTO – A new study out of Sick Kids Hospital in Toronto offers both hope and certainty to those suffering from Huntington’s disease, potentially shedding light on how the condition will progress in a patient.

By studying the causes of Huntington’s disease in mice, an international research team at the Hospital for Sick Children believes it may be possible to predict the disease’s progression in human beings.

“Today, understanding why Huntington’s disease progresses fast or slowly in different patients is mostly guesswork,” said Dr. Chris Pearson, lead author of the Sick Kids study. “Our research could allow us to predict how the disease will affect individual patients.”

Huntington’s disease affects an estimated five to 1 out of every 10,000 people worldwide, according to Huntington’s disease Society of America. The genetic disorder is hereditary – it is passed from parent to child – and its trajectory is unique to every patient.

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Symptoms include loss of physical and muscular coordination, cognitive decline, and eventually psychiatric problems, such as dementia.

The findings also extend to 40 different neurodegenerative disorders, including muscular dystrophy and Friedreich’s ataxia.

Difficulty in forecasting path of Huntington’s disease in patients

Because of the chaotic and unpredictable nature of these diseases, doctors today can’t predict how the disease will run its course. Symptoms could take decades to manifest – or they could manifest before birth.

“The diseases I work on are related in that the disease is progressive as you go through the pedigree – the child has it worse than the parent, who has it worse than the grandparent,” Pearson told Global News.

“The mutation also changes as the individual ages. So when you look at individuals even in a family, one sibling will have the disease worse than another, and it will progress faster in them.”

He says this unpredictability often leaves families feeling like they’re in the dark.

“If you were a parent, you would like to know everything you can. Unfortunately, there is no real easy way to get a prognostic indication for these diseases.”

Studying gene that repairs DNA

Pearson’s team looked at the gene responsible for Huntington’s disease in mice who suffered from the disorder. Known as MSH3, the gene is normally responsible for repairing “broken” or mutated DNA. In certain DNA sequences, however, the gene actually causes the mutation rather than prevent it.

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The group was able to identify the gene that makes this mutation happen. In that gene was variants that can make the mutation progress faster or slower. This finding could hold the key to understanding how a patient’s condition will change.

It could even be done in a simple screening process.

“If we find what we found in mice also happens in humans, we can use gene analysis of the variant and say ‘hey, you have this variant, you’re more likely to have the mutation, or less likely, than this other variant.”

Such a prognosis could offer Huntington’s patients much more clarity when they are first diagnosed.

“Right now when genetic counselors identify someone with Huntington’s, we can’t tell you whether that disease will progress quickly or slowly,” said Polly Thompson, communications specialist at the hospital.

“If you’re 20 years old, for example, that’s critical information. You could be planning school, marriage, all sorts of things.”

The study’s findings are an important step, according to Pearson. His next steps are to consider how to stop the gene that causes these mutations.

“We’re looking to attack (MSH3) as a therapeutic target,” Dr. Pearson said. “You target it to stop the repeat mutation in Huntington’s, theoretically.”

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“We’d like to inhibit it, stop it in its tracks, and identify the wrench that goes into the machine.”

elton.hobson@globalnews.ca