Most people have heard of ALS from news stories. It is one of the most feared diseases in medicine.
For some families, the fear runs in the DNA, because a gene mutation can pass the risk from parent to child.
Now scientists have found a way to read that risk in blood.
A study in Nature Medicine, published on July 27, 2026, pinpointed 19 proteins that can estimate when ALS symptoms will begin in people who carry a disease-linked gene.
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Researchers at the University of Miami Miller School of Medicine led the work. The test was accurate to within about 1.6 years on average.
The panel is not meant for the general public. It is aimed at people with a known inherited risk, who make up roughly 5 to 10 percent of all ALS cases, according to MedlinePlus Genetics.
They know the disease may come
ALS gradually kills the motor neurons that control muscle movement. Once those cells are gone, they do not come back.
Most treatments work better the earlier they start. A reliable warning window is one of the field's biggest unmet needs.
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The problem for gene carriers has been uncertainty. They know the disease may come. They do not know when.
Some people with the same mutation stay healthy into old age. Others fall ill in their forties.
How the 19-protein signature was found
The Pre-fALS study began in 2007 under neurologist Michael Benatar and research professor Joanne Wuu. For nearly two decades the team has collected blood samples from people at elevated genetic risk.
For this analysis, researchers examined plasma from 137 participants. Of those, 33 went on to develop clinical ALS or the related condition frontotemporal dementia.
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The team screened more than 5,000 proteins in the samples. Machine learning then narrowed the list to the 19 proteins that best predicted when symptoms would appear.
One of them is a well-known marker of nerve damage. It is called neurofilament light chain, or NfL, and it leaks into blood when motor neurons start to break down. NfL levels climb in the months before symptoms become visible.
The 18 other proteins add context that NfL alone cannot provide. Together they estimate time to symptom onset across a window of six months to five years. The authors report an average error of 1.6 years.
Benatar described the finding in a statement from the University of Miami. "By studying blood samples from people at elevated genetic risk for ALS, we identified protein signatures that predict whether someone is going to phenoconvert in the relatively near future."
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Phenoconversion is the moment a gene carrier moves from healthy to clinically ill.
What this means for patients and trials
The practical use is not a frightening countdown. It is to point gene carriers toward the right moment for preventive treatment and clinical trials.
One such trial is already underway. ATLAS, run in partnership with Biogen, is testing whether tofersen can delay or prevent the first symptoms in people who carry an SOD1 gene mutation. Tofersen is the active ingredient in Biogen's ALS drug Qalsody.
SOD1 mutations cause 15 to 20 percent of familial ALS worldwide.
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A reliable timing tool could help doctors know who is about to need such a drug, and when.
For now, the 19-protein panel is a research tool, not a commercial test.
Anyone concerned about a family history of ALS should talk to a neurologist or a genetic counselor.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.