What Is Lambert-Eaton Myasthenic Syndrome?
Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disease that affects your ability to move. In this disease, your immune system attacks muscle tissue. This leads to difficulty walking and other muscular problems.
Symptoms can temporarily subside with exertion, but the disease can’t be cured. The condition can be managed with medication.
What Causes Lambert-Eaton Myasthenic Syndrome?
In an autoimmune disease, your body’s immune system mistakes your own body for a foreign object. Your immune system produces antibodies that attack your body.
In LEMS, your body attacks nerve endings that regulate the amount of acetylcholine your body releases. Acetylcholine is a neurotransmitter that triggers muscle contractions. Muscle contractions allow you to make voluntary movements such as walking, wiggling your fingers, and shrugging your shoulders.
Specifically, your body attacks a protein called voltage gated calcium channel (VGCC). VGCC is required for the release of acetylcholine. You don’t produce enough acetylcholine when VGCC is attacked, so your muscles are unable to work properly.
Many cases of LEMS are associated with lung cancer. Researchers believe that the cancer cells produce the VGCC protein. This causes your immune system to make antibodies against VGCC. These antibodies then attack both the cancer cells and the muscle cells.
Anyone can develop LEMS in their lifetime, but lung cancer may increase your risk of developing the condition. If there is a history of autoimmune diseases in your family, you may be at higher risk of developing LEMS.
What Are the Symptoms of Lambert-Eaton Myasthenic Syndrome?
The primary symptoms include leg weakness and difficulty walking. As the disease progresses, you will also experience:
- weakness in the facial muscles
- involuntary muscular symptoms
- dry mouth
- bladder problems
Leg weakness often improves temporarily upon exertion. This is because, as you exercise, acetylcholine builds up in large enough amounts to allow strength to improve for a short time.
LEMS leads to complications including:
- trouble breathing and swallowing
- injuries due to falling or problems with coordination
Diagnosing Lambert-Eaton Myasthenic Syndrome
To diagnose Lambert-Eaton Myasthenic Syndrome, your doctor will take a detailed history and perform a physical examination. Your doctor will look for:
- decreased reflexes
- muscle tissue loss
- weakness or trouble moving that gets better with activity
The following tests may be ordered to confirm the condition:
- blood tests: to look for antibodies against VGCC (anti-VGCC antibodies)
- electromyography (EMG): to test your muscle fibers by seeing how they react when stimulated. A small needle is inserted into the muscle and connected to a meter. You will be asked to contract that muscle, and the meter will read how well your muscles respond.
- nerve conduction velocity test (NCV): your doctor will place electrodes on the surface of your skin covering a major muscle. The patches give off an electrical signal that stimulates the nerves and muscle. The activity that results from the nerves is recorded by other electrodes and is used to determine how quickly the nerves react to stimulation and how healthy they are.
Treating Lambert-Eaton Myasthenic Syndrome
This condition cannot be cured. You will work with your doctor to manage any other conditions such as lung cancer. You will also take immunosuppressant drugs to quiet your immune system.
Other treatments include:
- Intravenous immunoglobulin (IVIg) treatment: Your doctor will inject a nonspecific antibody that calms the immune system.
- Plasmapheresis: Blood is removed from the body; the plasma is separated out, the antibodies are removed, and the plasma is returned to the body.
Symptoms can sometimes be relieved by drugs that work with your muscular system, including:
- Mestinon (pyridostigmine)
- 3, 4 Diaminopyridine (3, 4-DAP)
These medications are hard to obtain, and you should talk to your doctor to find out more information.
What Is the Long-Term Outlook?
The symptoms may improve by treating other underlying conditions, suppressing the immune system, or removing the antibodies from the blood. However, not everyone responds well to treatment.