Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder. In this condition, your body interferes with a chemical needed for nerve cells to “tell” your muscle fibers to contract. Muscle weakness is a common symptom. Many people with LEMS have small-cell lung cancer. Treatments include cancer treatments and medications to help improve nerve cell muscle communication.
Lambert-Eaton myasthenic syndrome (LEMS), also known as Eaton-Lambert syndrome and Myasthenic Syndrome of Lambert Eaton, is an autoimmune disorder. In this condition, your body’s own immune system attacks the contact point between motor nerves and muscles — the so-called neuromuscular junction. The damage at this contact point impairs signaling to your muscles, causing weakness. This weakness usually begins in your upper legs, but can come to involve other muscle groups in your arms, as well as muscles involved in breathing, swallowing and speech.
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Two groups of people develop Lambert-Eaton myasthenic syndrome.
About 60% of cases happen in people who have an underlying malignancy. The most common is small-cell lung cancer. Symptoms of LEMS can begin many months or years before the cancer develops or is diagnosed. People tend to be older, with a diagnosis around the age of 60. It’s more commonly seen in people assigned male at birth (AMAB) and in people with a history of using tobacco products.
In about 40% of LEMS cases, no underlying cancer is identified. These people tend to be diagnosed at two peaks: around the age of 35 and a second peak occurring at the age of 60. Both sexes tend to be equally affected in this group.
LEMS is rare in children.
While small-cell lung cancer is the most common malignancy associated with LEMS, other cancers have also been associated with the development of LEMS, including prostate cancer, thymoma and lymphoproliferative disorders. Given that LEMS can develop before a person may show signs of cancer, your healthcare provider should ensure you undergo a thorough assessment for cancer if they make the diagnosis of LEMS.
Scientists think there may be a genetic link to autoimmune diseases in general. Lambert-Eaton myasthenic syndrome is an autoimmune disease.
Lambert-Eaton myasthenic syndrome is a rare disease. Worldwide, it affects about 2.8 million people. In the U.S., about 400 people have LEMS.
Lambert-Eaton myasthenic syndrome symptoms include:
Lambert-Eaton myasthenic syndrome typically affects leg muscle strength (upper leg) first, followed by shoulder muscles, muscles of your hands and feet, muscles affecting your speech and swallowing, and eye muscles.
Early in the disorder, you may have trouble getting up from a chair, walking up stairs or a steep walkway, or doing anything strenuous with your legs.
Symptoms usually develop slowly over weeks to many months. Symptoms develop more quickly if you have cancer and LEMS.
Lambert-Eaton myasthenic syndrome is an autoimmune disorder. This means your body’s natural defenders (antibodies) attack your own healthy tissue. In LEMS, your antibodies attack where nerve cells meet muscle fibers (neuromuscular junction); more specifically, at calcium channels that are critical in signaling at this contact point.
Like a lineup of dominoes, the attack causes a sequence of events:
LEMS happens in people who have small-cell lung cancer. In this case, your body’s antibodies recognize their “call to action” when there’s cancer in your body. However, instead of attacking the cancer cells (specifically, the calcium channel on cancer cells), it attacks the calcium channel at the end of nerve cells. And the sequence listed above happens. When this happens, your muscle cells can’t pick up the message to contract to make your muscle move.
Scientists think the cause of LEMS in people who don’t have lung cancer is an immune response that simply goes awry. It remains unclear why this happens.
The first step in the diagnosis of LEMS is a thorough evaluation by your healthcare provider, in most cases a general neurologist or a neurologist who specializes in disorders of nerves and muscles. A detailed history of your symptoms, as well as a review of your medical and medication history, is part of this process. A detailed neurological examination is often done to look for patterns of weakness and signs consistent with a diagnosis of LEMS.
The next step in the evaluation is testing. Testing for LEMS includes:
LEMS can appear from months to up to six years before the cancer does. The typical lung cancer screening schedule is every three to six months for at least two years after your diagnosis. Your healthcare provider will recommend a screening schedule that’s appropriate for you.
Lambert-Eaton myasthenic syndrome (LEMS) treatments include:
The exact cause of Lambert-Eaton myasthenic syndrome isn’t completely understood. So it’s not entirely known if there’s any way to prevent the disorder.
However, because LEMS can occur in people who have lung cancer, you can help prevent lung cancer by:
You can also take steps to maintain a healthy lifestyle, including:
There isn’t a cure for Lambert-Eaton myasthenic syndrome. Treatment for an underlying cancer associated with LEMS has been shown to improve LEMS-related symptoms. Immunosuppressive drugs can help control the autoimmune attack, as well as control symptoms along with symptomatic treatments that improve muscle strength by increasing the amount of acetylcholine at the nerve endings
If you have LEMS without cancer, you can expect a near-normal length of life. If you have LEMS and a cancer that was found early and managed, your symptoms may improve over time (but not to full recovery).
Your quality of life largely depends on the severity of your symptoms.
Contact your healthcare provider any time your health changes or your symptoms worsen.
Lambert-Eaton myasthenic syndrome and myasthenia gravis share some similar symptoms. They both cause muscle weakness and rapid muscle fatigue.
Myasthenia gravis commonly affects the muscles around your eyes and muscles used for swallowing first. Then, it can affect muscles more generally, including breathing muscles and muscles of your arms and legs.
LEMS usually begins with weakness in your upper legs and later involves your arms. LEMS can cause weakness of eye muscles, but this is usually mild compared to myasthenia gravis.
Severe respiratory muscle weakness (muscles that help you breathe) can be fatal in MG. This is rare in LEMS.
People with MG don’t often show signs of autonomic dysfunction such as dry eyes, dry mouth, constipation, decreased sweating and impotence. In contrast, people with LEMS more commonly have these complaints and can sometimes help in differentiating between the two conditions.
A note from Cleveland Clinic
Lambert-Eaton myasthenic syndrome (LEMS) is a disease caused by an immune system that has gone awry. Your nerve cells aren’t sending enough “messages” telling your muscle fibers to contract. The result is muscle weakness and other symptoms. Small cell lung cancer is present in about 60% of people with LEMS. If you have LEMS, but don’t have cancer, make sure you and your provider are scheduling cancer screenings every few months for at least two years after your diagnosis. Treatments include treating cancer (if it’s present) and taking medications that help increase nerve cell-muscle fiber communication. Increasing communication improves muscle strength and other symptoms.
Last reviewed by a Cleveland Clinic medical professional on 05/21/2022.
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