Lambert-Eaton myasthenic syndrome (LEMS) causes the body to attack nerves, resulting in muscle weakness in the arms and legs. It often occurs due to underlying conditions such as small cell lung cancer.

LEMS is an autoimmune condition, meaning the body’s immune system attacks nerve cells. This attack affects how nerve cells communicate with muscle cells, leading to symptoms of weakness and fatigue in the affected muscles.

This article discusses LEMS, including its symptoms, causes, diagnosis, treatment options, and how it differs from similar conditions.

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LEMS, also known as Lambert-Eaton syndrome (LES), is a rare autoimmune disorder that affects 2.8 per million people worldwide. It mostly affects individuals over the age of 50 years but can also affect children.

In the United States, there are approximately 400 known cases of LEMS.

In LEMS, the body’s immune system attacks the neuromuscular junction, which is where nerve cells meet muscle cells. This attack impairs nerve cells’ ability to release acetylcholine, a chemical essential for muscle contraction. The result is muscle weakness and fatigue, particularly in the arms and legs.

The symptoms of LEMS develop gradually over several weeks to months. They can vary in severity.

Common symptoms include:

  • Muscle weakness or aching: It primarily affects the proximal muscles, such as those in the hips, thighs, shoulders, and upper arms. Muscle weakness often improves temporarily after exercise.
  • Fatigue or tiredness: This mainly affects muscles in the arms and legs.
  • Reduced tendon reflexes: This might refer to an absent response to a sudden muscle stretch. Such a response suggests potential issues with a muscle or the peripheral nervous system.
  • Autonomic dysfunction: Symptoms such as dry mouth, constipation, and erectile dysfunction may occur due to the involvement of the autonomic nervous system.
  • Difficulty walking or swallowing: Due to muscle weakness, people with LEMS may have issues with mobility and balance, such as climbing stairs. Individuals may also experience swallowing issues.
  • Respiratory failure: This is a relatively rare occurrence, often associated with the advanced stages of LEMS. Respiratory failure prevents the lungs from releasing enough oxygen into the blood.

LEMS is a paraneoplastic syndrome, meaning it occurs when the body’s immune system mistakenly attacks and damages the nerves in response to tumors.

For 50% to 60% of cases, the underlying cause is small cell lung cancer (SCLC). However, LEMS can also result from nonparaneoplastic causes and may occur due to another autoimmune disorder.

In LEMS, the body attacks the calcium channels on nerve endings at the neuromuscular junction. Still, the cause of some cases of LEMS is not known.

Diagnosing LEMS requires a combination of tests, including:

  • Clinical assessment: A doctor will examine a person’s medical history and perform a physical exam focusing on muscle strength and fatigue.
  • Serology: This is a specialized test that detects antibodies (or proteins) to calcium channels on nerve cells. Around 85% to 95% of people with LEMS may present with these antibodies.
  • Electrodiagnostic testing: Electromyography and repetitive nerve stimulation can detect electrical irregularities in muscle response.
  • Imaging studies: A CT or MRI scan can help identify any underlying cancer, especially SCLC.

Treatment for LEMS focuses on managing symptoms and addressing any underlying conditions. It usually involves a combination of medication and physical therapy to maintain muscle strength and improve mobility.


A doctor will evaluate a person’s symptoms and prescribe medications, such as:

  • 3,4-Diaminopyridine (3,4-DAP): This medication helps increase the release of acetylcholine, which can improve nerve-muscle communication.
  • Intravenous immunoglobulin (IVIG): IVIG is the main treatment for severe cases that do not respond to other treatments. It neutralizes harmful antibodies and helps regulate immune cells.
  • Immunosuppressants: Medications such as prednisone or azathioprine can hamper the immune system and prevent it from attacking nerve cells.
  • Cancer treatment: If LEMS is paraneoplastic, treating the underlying cancer is crucial. Doing so often improves neuromuscular symptoms.
  • Plasmapheresis: This procedure filters the blood to remove the affected plasma attacking the nerves and replaces it with healthy plasma.

Living with LEMS requires a multidisciplinary approach to help manage symptoms and maintain quality of life.

A person may benefit from:

  • Regular medical follow-ups: A doctor can monitor disease progression and adjust treatment plans.
  • Supportive therapies: This can include occupational therapy that helps enhance daily functioning.
  • Lifestyle adjustments: This can include incorporating rest periods to manage fatigue and avoiding activities that may exacerbate symptoms.
  • Psychological support: Counseling or support groups to cope with the emotional and psychological effects of LEMS.

The outlook for LEMS varies depending on the underlying cause and effectiveness of treatment. With appropriate management, many people experience significant improvement in symptoms.

However, in cases with co-occurring cancer, the outlook largely depends on the cancer’s stage and response to treatment. Early detection and intervention are essential for improved outcomes.

Currently, no known methods prevent LEMS. However, early detection and treatment of cancers — particularly SCLC — can reduce the risk of developing paraneoplastic LEMS.

Regular health check-ups and monitoring for symptoms in high risk individuals are advisable.

LEMS and myasthenia gravis (MG) are both autoimmune neuromuscular disorders. They present with similar symptoms, such as muscle weakness and fatigue. However, they have distinct differences. In MG, the immune system attacks a different nerve than in LEMS.

People with LEMS experience muscle weakness that temporarily improves with repeated activity. However, for people with MG, muscle weakness usually worsens with exercise or repeated use.

Additionally, MG symptoms can affect the muscles of the eye, which can cause drooping eyelids and double vision. LEMS is less likely to affect eye muscles and more likely to affect muscles in the arms or legs.

Another difference is that LEMS frequently occurs in individuals with SCLC, while MG has links with thymoma or other thymic issues.

What causes Lambert-Eaton myasthenic syndrome?

LEMS occurs when the immune system mistakenly attacks calcium channels on nerve endings. It often occurs due to certain cancers, such as SCLC, or other autoimmune conditions.

What is the cure for Lambert-Eaton myasthenic syndrome?

There is no cure for LEMS, but treatments can effectively manage symptoms and improve quality of life. These include medications, immunosuppressants, and treating any underlying causes, such as SCLC.

What is the life expectancy for Lambert-Eaton myasthenic syndrome?

Life expectancy varies based on the underlying cause and response to treatment.

Where cancer is not the cause, LEMS does not affect a person’s life expectancy. A person with cancer may have a life expectancy that depends on the cancer’s stage and treatment success.

Lambert-Eaton syndrome (LEMS) is a rare autoimmune disorder that causes muscle weakness and fatigue. It primarily affects muscles in the arms and legs. Underlying cancer, especially SCLC, can cause LEMS.

Diagnosis involves clinical evaluation, electrodiagnostic studies, and blood tests. Treatment focuses on managing symptoms and addressing the root cause.

While there is no cure, effective treatments can significantly improve quality of life. Early detection and a multidisciplinary approach are key to managing LEMS effectively.