Lambert-Eaton Syndrome: A Rare Autoimmune Disorder Explained

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People with LEMS have antibodies that attack the part of nerve endings that send signals to muscles. This reduces the release of acetylcholine and weakens the signal to muscle cells. This causes symptoms of proximal muscle weakness, absent deep tendon reflexes, and autonomic dysfunction. The condition can occur as a paraneoplastic disorder associated with malignancy (CA-LEMS) or without cancer as an autoimmune disease (NCA-LEMS).

Symptoms

In this condition, your immune system makes autoantibodies that attack the neuromuscular junction, where nerve cells connect to muscles. This prevents them from sending the signals that control muscle movement. The weakness begins in the muscles that help you stand and walk but can affect other body parts as it progresses. Your healthcare provider may ask you what is Lambert-Eaton syndrome to gauge if you are aware of this condition. Your healthcare provider may diagnose Lambert-Eaton Syndrome by asking about your symptoms and doing a physical exam. Lambert-Eaton Syndrome can occur either as a paraneoplastic disorder associated with underlying cancer (CA-LEMS) or without it as part of a general autoimmune state (NT-LEMS). In the case of CA-LEMS, the cancer is usually small-cell lung cancer. But it can also be cancer of the prostate thymoma or any other type of cancer. In up to 60 percent of cases, the onset of LEMS precedes the cancer diagnosis. Patients with LEMS have insidious and progressive proximal muscle weakness, reflexes that do not facilitate after brief exercise and autonomic dysfunctions. Many clinical symptoms overlap with other myasthenic disorders, especially myasthenia gravis, which may result in misdiagnosis or delayed diagnosis. Treatments for this condition can include medications that suppress your immune system and medicines that improve the signals between nerve cells and muscle cells. It is essential to get regular checkups and have your home tested for radon, a known carcinogen that increases the risk of lung cancer in people with this condition.

Diagnosis

LEMS damages the part of the nerve ending that releases acetylcholine, which weakens the signal from the nerve to the muscle. It affects the muscles in your legs and arms but not those in your head (cranial nerves). Weakness develops slowly over weeks to months and gets worse if cancer is present. Your doctor diagnoses this rare condition based on your symptoms and history. You may have an electromyography test that uses needles to measure how quickly signals go from the nerves to your muscles. This can help determine if your weakness is due to cancer or a different condition, such as myasthenia gravis. The antibodies in LEMS attack the point where the nerves meet the muscle fibers (neuromuscular junction). The antibodies bind to and block calcium channels at the end of the nerve cells, which reduces the amount of acetylcholine released. Acetylcholine is necessary to send a strong signal to the muscles to activate. About half of people with LEMS have an associated tumor, usually small-cell lung cancer. The other half have a paraneoplastic disorder caused by substances made by the tumor and by the body’s immune response to the tumor. This type of LEMS typically appears before, during, or after the cancer treatment that is being used.

Treatment

In some cases, Lambert-Eaton syndrome is associated with a type of cancer called small-cell lung cancer. This form of the condition is called paraneoplastic LEMS. In other cases, it happens without an underlying cancer and is considered non-paraneoplastic LEMS. This condiLambert-Eaton Syndrome: A Rare Autoimmune Disorder Explainedtion attacks the point where nerve cells meet muscle fibers to send signals that help muscles move. Specifically, antibodies attack the calcium channels at the end of nerve cells. As a result, less of the chemical acetylcholine is released. This reduces the strength of the signal that muscles receive, and it causes them to feel weak. Symptoms start slowly and worsen over weeks to months. They develop in your hip girdle and thigh muscles first, then spread to your arms and shoulders. Weakness is most noticeable when you try to stand, walk, or climb stairs. Weakness can also affect your breathing and blood pressure control.

Several ways to treat LEMS include plasma exchange and high-dose immunoglobulin therapy. Plasma exchange involves separating the liquid part of your blood (plasma) from your blood cells and then recombining it with new plasma that does not contain any of your antibodies. Your healthcare provider may recommend this treatment if you have severe symptoms that medications cannot control. High-dose immunoglobulin therapy is a treatment that gives you high amounts of the antibody-blocking protein immunoglobulins. This helps your body fight the autoimmune response that’s causing your symptoms.

Prevention

Lambert-Eaton syndrome happens when your body’s immune system attacks the connections between nerves and muscles. It can happen with cancer (paraneoplastic LEMS or CA-LEMS) or without cancer as part of a general autoimmune state (NCA-LEMS). The most common symptoms are weak muscles, trouble walking, and tingling sensations. Cancer treatment often improves this condition, but medicines to suppress the immune system or to help strengthen the signals between nerves and muscles also may help. The first step in diagnosis is a thorough evaluation by your healthcare provider, usually a neurologist specializing in nerves and muscle disorders. This includes a review of your health history and an exam. A blood test can find the antibodies that cause the condition. These antibodies bind to calcium channels at the nerve cells’ end, interrupting their signaling. This causes the loss of the muscle-strengthening chemical acetylcholine. Symptoms of Lambert-Eaton syndrome develop slowly over weeks or months, although they may come on more quickly in people with cancer. They affect the legs, arms, chest, neck, throat, and the muscles needed for breathing and swallowing. LEMS occurs more frequently in people with small-cell lung cancer but can occur in people without or with a different type of cancer. The connection between cancer and this condition isn’t clear, but researchers think your immune system responds to cancer by attacking the same calcium channels at the ends of nerve cells.

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