LEMS Overview: A Patient's Perspective
The purpose of this section is to provide a comprehensive overview of published and currently in-use treatments for Lambert-Eaton Myasthenic Syndrome (LEMS), to provide references to sources that provide further details, and to describe the experiences of some LEMS patients with these treatments.
This article does not provide medical advice, which should always be obtained from qualified medical professionals who know the patient.
The LEMS patients whose experiences are described in this article are a self-selected group that participates in monthly video conferences that are organized through the Lambert-Eaton LEMS Family Association and the Lambert-Eaton News site. About 5 to 15 patients participate in each of the video conferences.
We cannot claim that this group represents LEMS patients in general. We will refer to this group as the LEMS meeting group in the remainder of this article. The brief overview of the pathophysiology of LEMS in the following three paragraphs will help the reader understand the purpose of different LEMS treatments. Reference [1] in the list on this page gives further details on this topic.
Lambert-Eaton Myasthenic Syndrome Overview and Explanation
What is LEMS?
Lambert-Eaton myasthenic syndrome (LEMS) is a very rare condition that affects the signals sent from the nerves to the muscles. Muscles are unable to contract properly, resulting in muscle weakness and a range of other symptoms.
The immune system attacks the neuromuscular junctions – the areas where nerves and muscles connect.
LEMS is often associated with a certain type of cancer (SCLC, or Small Cell Lung Cancer). LEMS may result from the body’s effect to fight the underlying cancer.
In some remaining cases, LEMS develops following another autoimmune disease. Sometimes the cause is not known.
What are the symptoms of LEMS?
LEMS affects how nerves and muscles communicate, leading to muscle weakness and other body system changes. Symptoms often include:
Muscle Weakness
- Weakness in the hips and thighs (trouble standing up, climbing stairs, or walking)
Weakness in the shoulders and upper arms
Legs are usually affected before arms
Strength may temporarily improve after brief activity, then worsen again
Fatigue
Ongoing, heavy fatigue not relieved by rest
Autonomic (Involuntary) Symptoms
Dry mouth
Constipation
Erectile dysfunction
Reduced or absent sweating
Blurred vision
Reflex Changes
Decreased or absent reflexes (like knee-jerk reflex)
Other Possible Symptoms
Difficulty speaking or swallowing (less common than in MG)
Eye symptoms like droopy eyelids (usually mild or absent)
How does LEMS affect the nerves and muscles?
Autoantibodies are antibodies in an individual’s immune system that attack healthy parts of that individual’s body instead of fighting disease. Most LEMS patients produce autoantibodies that that attack P/Q type voltage-gated calcium channels (VGCCs) on the endings of nerves that communicate with muscles, and some produce autoantibodies that attack N type VGCCs [2]. These antibodies are created by plasma B cells, which also create normal antibodies of the IgG group.
The effect of these autoantibodies is to reduce the capacity of the nerve endings to produce the neurotransmitter (acetylcholine) that signals adjacent muscle fibers to contract, resulting in muscle weakness. Another possible effect is to disrupt the autonomic nervous system, resulting in symptoms such as dry mouth, constipation, erectile dysfunction, and impaired sweating.
Autoantibodies that attack P/Q or N type VGCCs cannot be detected in the blood of some LEMS patients (who have nevertheless been diagnosed with LEMS on the basis of other criteria), which suggests that these patients produce one or more different, unrecognized types of autoantibodies. These LEMS patients are referred to as seronegative. The nerve endings, the receptors on the muscles that detect the neurotransmitter released by the nerve endings, and the gap between them are collectively referred to as the neuromuscular junction.
What is treatment for cancer in cases where LEMS is associated with cancer?
LEMS is sometimes associated with cancer, possibly very early stage. In this case, LEMS is referred to as a paraneoplastic syndrome. The type of associated cancer is most commonly small cell lung cancer. However, other types of cancer may also be associated with LEMS. References [3] and [4] provide further details on this topic.
If a cancer diagnosis accompanies a LEMS diagnosis, then treatment for the cancer is necessary alongside treatment for LEMS. If no cancer is detected when LEMS is diagnosed then the patient may be put on a cancer screening protocol that can last for multiple years, in case that patient has a very early stage cancer that is not detectable. The screening protocol can vary depending on the experience and judgment of the patient’s medical team, the age of the patient, and the cancer risk factors that the patient has been exposed to. Reference [4] describes one set of cancer screening guidelines for conditions that are possibly paraneoplastic syndromes, including LEMS.
Some members of the LEMS meeting group have reported that their cancer screening is planned to last for up to 5 years, in contrast to the 2 years of the LEMS-related screening described in [4].
