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Researchers have discovered a common problem that leads to all forms of amyotrophic lateral sclerosis (ALS), an important finding that could potentially lead to future treatment breakthroughs for the fatal neurodegenerative disease.

ALS, often called Lou Gehrig's disease after the New York Yankees baseball player who was diagnosed with it in 1939, is known for its unforgiving progression and devastating consequences, and for the mystery that surrounds its causes.

An estimated 10 per cent of cases are believed to be hereditary, and researchers have already discovered the genetic mutations that account for 30 per cent of familial ALS cases. The other 90 per cent of ALS cases are sporadic, meaning they have no ties to family history.

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This has baffled researchers who have been trying for years to understand the apparent multitude of genetic and environmental causes that lead to the development of the disease.

Now, researchers have identified a common pathway – a disturbance or breakdown – in the proper functioning of a protein believed to be critical in recycling damaged proteins can lead to all forms of ALS. The breakdown causes other damaged proteins to build up in neurons of the brain and spinal cord, leading to the degeneration that results in the disease. "I think this pathway is the key," said Teepu Siddique, lead author of the study and the Les Turner ALS Foundation/Herbert C. Wenske Foundation professor in the department of neurology and clinical neurosciences at Northwestern University's Feinberg School of Medicine in Chicago.

Denise Figlewicz, vice-president of research at the ALS Society of Canada, said the findings confirm what many in the field have suspected for years.

"It's not like this is opening a whole new vista," she said.

While significant, confirmation that a protein breakdown is a common pathway for ALS doesn't fully explain how the problem develops or what else may be involved, she said. It's clear much more work is needed, but these findings prove researchers are on the right track, she said.

There are an estimated 2,500 to 3,000 Canadians living with ALS, a disease characterized by progressive paralysis that eventually restricts the ability to do even basic tasks, such as speaking, swallowing and, eventually, breathing. In many cases, patients' cognitive function remains intact.

In the study, researchers studied the genes of a five-generation family with ALS and discovered the common protein breakdown. They then examined cases of sporadic ALS, which confirmed the presence of the protein breakdown.

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Dr. Siddique noted that while families with a history of ALS carry the protein mutation, not all members develop the disease. That means there is some element at play protecting those people, an anomaly researchers will now focus on in the hopes of developing an effective treatment.

Kym Boycott, a neurogeneticist at the Children's Hospital of Eastern Ontario in Ottawa, said the findings could also go a long way toward aiding the understanding of early onset ALS, which occurs very rarely in children.

She also noted that, as is the case with many rare diseases, studying ALS has been a long and challenging process for researchers that has yet to yield effective therapies for patients.

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