Lou Gehrig’s disease, formally called amyotrophic lateral sclerosis (ALS), is a progressive neurological condition that destroys the nerve cells responsible for voluntary movement. It affects roughly 33,000 people in the United States at any given time, and that number is expected to rise above 36,000 by 2030. The disease is named after the famous New York Yankees first baseman who was diagnosed in 1939.
ALS targets two groups of nerve cells called motor neurons. One group runs from the brain down to the spinal cord (upper motor neurons), and the other extends from the spinal cord out to muscles throughout the body (lower motor neurons). As both groups gradually deteriorate and die, they stop sending signals to muscles. The muscles weaken, waste away, and eventually stop working entirely. Critically, ALS typically spares thinking ability, meaning most people remain mentally sharp as their bodies lose function.
How Symptoms Begin
ALS usually starts in one of two ways. About 70 to 74% of cases are “limb onset,” meaning the first symptoms appear in the arms or legs. Early signs include muscle cramps or stiffness, twitching, weakness in the hands or ankles, and loss of grip strength. You might notice trouble with everyday tasks like buttoning a shirt, writing with a pen, or walking without tripping.
The remaining cases are “bulbar onset,” where symptoms first affect the face and throat. These include slurred speech, difficulty chewing and swallowing, excessive choking, and twitching in the tongue, jaw, or throat muscles. A person’s voice may become harsh, hoarse, or strained, and their speech may lose clarity or volume. Bulbar-onset ALS tends to progress faster than limb-onset cases.
Regardless of where it starts, ALS eventually spreads to other parts of the body. Muscles that were initially unaffected gradually weaken over months and years. Breathing muscles are typically the last major group involved, and respiratory failure is the most common cause of death.
Causes and Risk Factors
For the vast majority of people with ALS, there is no clear inherited cause. About 95% of patients have no affected first-degree relatives, a pattern called sporadic ALS. The remaining cases are familial, meaning the disease runs in the family through identifiable genetic mutations.
The most common genetic culprit is a mutation in a gene called C9orf72, which accounts for 30 to 60% of familial cases depending on the population. A smaller number of familial cases involve mutations in the SOD1 gene (relevant because it’s now treatable) and several others. The line between sporadic and familial ALS is blurrier than it once seemed: roughly 8% of people with no family history of the disease also carry the C9orf72 mutation, suggesting genetics play a role even in seemingly random cases.
Beyond genetics, known risk factors include age (most people develop ALS between 40 and 70), being male (slightly higher risk), and possibly environmental exposures, though no single environmental cause has been definitively proven.
How ALS Is Diagnosed
There is no single blood test or scan that confirms ALS. Diagnosis relies on clinical evaluation, nerve conduction studies, and a process of ruling out other conditions that can mimic its symptoms, such as spinal cord compression or autoimmune disorders. This process often takes months, which is one reason diagnostic delays are common.
Doctors use standardized criteria to classify the likelihood of ALS. The newest framework, called the Gold Coast Criteria, was introduced in 2020 to simplify diagnosis and catch the disease earlier. It detects ALS correctly in about 94% of cases, a meaningful improvement over older systems that caught only 56 to 86% of cases at higher certainty levels. Electromyography (EMG), a test that measures electrical activity in muscles, is a key part of the workup because it can reveal damage to motor neurons before symptoms become obvious.
Life Expectancy and Prognosis
ALS life expectancy typically ranges from 2 to 5 years after symptoms first appear. One recent longitudinal study found a median survival of 53 months from symptom onset. But averages obscure wide variation. Some people live a decade or longer, while others, particularly those with bulbar onset, decline more rapidly. Age at diagnosis, how quickly symptoms spread in the first year, and respiratory function at the time of diagnosis all influence the timeline.
Treatment Options
No treatment cures ALS or reverses the damage it causes. The medications that exist aim to slow progression modestly or target specific genetic forms of the disease.
Riluzole, the oldest approved therapy, extends survival by a few months on average. It works by reducing the activity of a chemical messenger that can overstimulate and damage nerve cells. Edaravone, given by infusion or taken orally, acts as an antioxidant and may slow functional decline in some patients, though its benefit has been debated.
The most targeted therapy to date is tofersen (brand name Qalsody), approved for ALS caused by SOD1 gene mutations, which account for about 2% of all cases. Tofersen works by blocking production of the harmful SOD1 protein, and studies show it can stabilize decline and even improve strength and mobility in some people. It is delivered directly into the spinal fluid.
One drug that is no longer available is Relyvrio, which was pulled from the market in late 2024 after a large Phase 3 trial failed to show benefit. The FDA formally withdrew its approval in August 2025.
Supportive Care and Quality of Life
While medications offer limited benefit, multidisciplinary care teams have a significant impact on both survival and quality of life. Specialized ALS clinics coordinate neurologists, respiratory therapists, physical therapists, speech therapists, nutritionists, and social workers in a single visit. Studies consistently show that this model leads to fewer hospital stays, fewer emergency procedures, and better overall outcomes. Patients treated at multidisciplinary clinics are also more likely to receive interventions at the right time rather than in crisis.
Non-invasive ventilation, a mask-based breathing support worn mainly at night, is one of the most important supportive tools. It prolongs survival and can meaningfully improve quality of life when introduced at the right stage, before breathing muscles have weakened severely. A feeding tube may also be recommended when swallowing becomes difficult, helping maintain nutrition and reduce choking risk.
Communication Technology
As ALS affects speech, augmentative and alternative communication devices become essential. Early options include picture boards and portable computers with text-to-speech software. As hand function declines, eye-tracking devices allow a person to select letters, words, or phrases on a screen using only eye movement, and the computer speaks the message aloud. These systems require the ability to control eye movement, which ALS typically preserves until very late stages. Medicare has covered speech-generating devices since 2001, making them accessible to most patients. For many people living with ALS, these tools are the difference between isolation and continued connection with family, caregivers, and the world.