Some people recover from ALS — now, we might know why

It's exceedingly rare, but some patients with the deadly neurological disease amyotrophic lateral sclerosis (ALS) eventually recover — and now, scientists know why.

"More research needs to be done for sure before we can say confidently, but this is an exciting breakthrough that could lead to new efficacious treatments," Dr. Jesse Crayle, lead study author and a neurologist at Washington University in St. Louis, told Live Science in an email.

Around 5,000 new patients are diagnosed with ALS in the U.S. every year. The disease damages nerves in the brain and spinal cord that control the voluntary movement of muscles, including those that support breathing. Early ALS symptoms include muscle twitching and cramping, and over time, the disease progresses, causing patients to have difficulty chewing food, speaking and eventually, breathing. Respiratory failure causes most patients to die within three to five years of their symptoms beginning.

The U.S. Food and Drugs Administration (FDA) has approved several drugs to manage ALS symptoms, such as riluzole, which slows the nerve damage caused by the disease. However, there are currently no treatments that can cure the disease.

Related: 11 children diagnosed with new form of ALS

To try and find a solution, researchers have turned their attention to a rare subset of patients with ALS who partially or completely recover from the disease. Until now, it was unknown why these patients, who constitute less than 1% of cases, are able to do this. Yet their recoveries could provide clues as to how the disease can be treated.

In a new study, researchers analyzed DNA from saliva samples collected from 22 people who had been diagnosed with ALS but spontaneously recovered.