Lambert-Eaton syndrome (LEMS) and myasthenia gravis (MG) are autoimmune conditions that affect how the nerves communicate with muscles, leading to muscle weakness.
However, they are separate conditions with different causes, symptoms, and treatments.
This article identifies the differences and similarities between LEMS and MG and how to distinguish between them.
A note about sex and gender
Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.
LEMS is a rare condition that affects a person’s motor neurons, which are the nerves that control movement. They produce the neurotransmitter acetylcholine, which enables the muscles to work correctly.
In LEMS, the nerves are unable to produce acetylcholine effectively. This affects how well the muscles work, leading to muscle weakness, which begins in the limbs.
LEMS results from an autoimmune condition in which the immune system attacks the channels that produce acetylcholine. In
Learn what other autoimmune diseases have links to lung cancer.
MG is another autoimmune condition that leads to muscle weakness. It also involves problems with the neurotransmitter acetylcholine.
In MG, antibodies stop the muscles from receiving acetylcholine. This prevents nerve signals from reaching the muscles, resulting in muscle weakness in the face and neck.
MG
MG may occur when the thymus gives incorrect instructions to the nervous system, possibly due to benign (noncancerous) tumors.
Learn about the difference between MG and multiple sclerosis.
It can be challenging to distinguish between
| Feature | LEMS | MG |
|---|---|---|
| Who it affects | 60% to 75% of people with LEMS are male. The peak in onset is around age 35 and then again over 60. | Can occur at any age, especially females under 40 and males over 60. |
| Common early signs | often limb weakness | often eye muscle weakness |
| Symptom location | mainly affects the limbs, but rarely the face | mainly affects the facial muscles and swallowing |
| How common it is | 46 times less common than MG | affects 5 to 14 people per 100,000 |
A doctor can use various tests to diagnose LEMS or MG, such as:
- blood tests to identify antibodies
- muscle function tests
- nerve conduction tests
- CT or MRI scans to look for tumors or to check the thymus
The results can help confirm if a person has MG or LEMS.
Read more about the other causes of muscle weakness.
MG and LEMS both involve muscle weakness, but there are differences in the symptoms. The symptoms of LEMS may include:
- weakness in the arms and legs
- heaviness in the legs
- problems with automatic body functions leading to:
- dry mouth
- constipation
- bladder problems
- heart palpitations
- erectile dysfunction in males
Learn more about the symptoms of LEMS.
The symptoms of MG
- eye muscle weakness
- drooping eyelids
- blurred vision or double vision
- changes in facial expression
- speech changes
- difficulty swallowing
- weakness in the limbs, fingers, and neck
- breathing problems
The treatment options for MG and LEMS are different, but they can overlap.
Treatment options for LEMS
If LEMS results from a tumor or
A doctor may also recommend medications, such as:
- drugs to balance neurotransmitters and improve nerve and muscle function
- high dose intravenous immune globulin, a drug that temporarily neutralizes certain antibodies
- steroid drugs and other immunosuppressants to dampen the effect of the immune reaction
- plasma exchange, in some cases
Treatment options for MG
For MG, a doctor
- drug treatment to improve nerve signals and increase muscle strength
- immunosuppressive drugs to reduce immune system activity, in some cases
- surgery to remove the thymus gland (thymectomy)
Some factors may improve or worsen MG. An infection, fever, or reaction to certain medications can lead to a crisis. If symptoms become severe, a person may need:
- short-term treatments, such as plasma exchange
- high dose intravenous immune globulin to temporarily improve severe muscle weakness
- use of a respirator, in some cases
Some medications, such as statins,
Learn moreHere are some other medications for MG:
LEMS and MG can affect a person’s quality of life but not necessarily their life expectancy.
LEMS
When LEMS does not stem from cancer, life expectancy is similar to that of the general population. The survival rates for people with cancer-related LEMS will depend on the type and stage of cancer, among other factors.
The average life expectancy for people with both LEMS and SCLC appears to be longer than for those with SLCL alone. According to a
Treatment can make a big difference to quality of life. At diagnosis, around
Learn more about life expectancy with SCLC.
Myasthenia gravis
Most people with MG will live as long as those without MG.
According to a
Factors affecting the outlook include the risk of aspiration pneumonia and the adverse effects of certain medications.
Learn more about tests for MG.
Here are some questions people often ask about LEMS and MG.
What is the difference between MG and LEMS?
MG and LEMS both involve muscle weakness, and both are autoimmune conditions. However, the causes are different. LEMS is more likely to stem from cancer, whereas MG may occur due to problems with the thymus.
They also have different symptoms. MG tends to affect the face and neck, whereas LEMS usually starts in the limbs.
What is the life expectancy of someone with LEMS?
Many people with LEMS have the same life expectancy as those without LEMS. However, if LEMS results from cancer, the life expectancy will depend on the cancer.
LEMS and MG are autoimmune conditions that involve muscle weakness. However, there are some key differences.
LEMS often stems from lung cancer, while MG can involve noncancerous tumors or problems with the thymus gland. LEMS tends to involve limb weakness, while MG mainly affects the face and neck muscles.
With modern treatments, people with MG or LEMS can live as long as those without these conditions. The only exception to this is when LEMS occurs due to cancer. In these situations, the outlook will depend on the type and stage of the cancer.