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Disease Profile

Lambert Eaton myasthenic syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-9 / 1 000 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

LEMS; Eaton Lambert syndrome; Lambert Eaton syndrome;


Musculoskeletal Diseases; Nervous System Diseases


Lambert Eaton myasthenic syndrome (LEMS) is a disorder of the neuromuscular junction. The neuromuscular junction is the site where nerve cells meet muscle cells and help activate the muscles.[1] This syndrome occurs when antibodies interfere with electrical impulses between the nerve and muscle cells. It may be associated with other autoimmune diseases, or more commonly coincide with or precede a diagnosis of cancer such as small cell lung cancer. Symptoms may include muscle weakness, a tingling sensation in the affected areas, fatigue, and dry mouth.[1] Treatment of an underlying disorder or cancer is the first priority of treatment.[2]


The signs and symptoms of LEMS usually appear around 40 years of age and are characterized by muscle weakness, dysautonomia (autonomic nervous system disorders), and decreased tendon reflexes.[3][4]

Muscle weakness may vary in severity and can lead to:[3]

  • Difficulty climbing stairs
  • Difficulty lifting objects
  • Need to use hands to arise from sitting or lying positions
  • Difficulty talking
  • Difficulty chewing
  • Drooping head
  • Swallowing difficulty, gagging, or choking

Vision issues may additionally occur including:[3]

  • Blurry vision
  • Double vision
  • Difficulty maintaining a steady gaze

Other symptoms may include blood pressure changes, dizziness upon rising, and dry mouth.[3]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Calcium channel antibody positivity
EMG: decremental response of compound muscle action potential to repetitive nerve stimulation
EMG: repetitive nerve stimulation abnormality
Progressive proximal muscle weakness
Reduced tendon reflexes
Dry mouth
Dry mouth syndrome
Reduced salivation

[ more ]

30%-79% of people have these symptoms
Bulbar signs
Difficulty getting a full erection
Difficulty getting an erection

[ more ]

Small cell lung carcinoma
5%-29% of people have these symptoms
Decreased ability to sweat
Decreased sweating
Sweating, decreased

[ more ]

Keratoconjunctivitis sicca
Dry eyes
Orthostatic hypotension due to autonomic dysfunction


LEMS is a disorder of the immune system, also known as an autoimmune disorder. Autoimmune disorders occur when the body's defense system against foreign organisms (antibodies) attack healthy tissue. LEMS occurs when part of the neuromuscular junction is damaged. The neuromuscular junction is the area between a nerve cell and a muscle cell, where communication occurs through the release of a chemical signal, called acetylcholine (ACh). This results in muscle contraction or movement. When individuals have LEMS, this process is blocked and ACh is not effectively released from nerve cells.[5][6]

In instances where LEMS is associated with cancer, the cause may be related to the body’s attempt to fight the cancer and accidental attack of nerve fiber endings, especially the voltage-gated calcium channels found there. The trigger for the cases not associated with cancer is unknown.[5][2]


There is no cure for LEMS. Treatment may vary depending on the individual's age, general health, and whether there is an associated cancer or autoimmune disorder. If cancer or an underlying autoimmune disorder is present, treatment should focus on these conditions first. They may result in symptom relief.[2][6]

Medications and therapies that may be used to treat Lambert-Eaton myasthenic syndrome include: 3,4-diaminopyridine (enhances acetylcholine release), anticholinesterase agents (e.g., Pyridostigmine), plasma exchange (where blood plasma is removed and replaced with fluid, protein, or donated plasma), intravenous immunoglobulins (IVIG), and medications that suppress the immune system (e.g., prednisone, azathioprine).[2]

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

  • Amifampridine phosphate(Brand name: Firdapse) Manufactured by Catalyst Pharmaceuticals, Inc.
    FDA-approved indication: November 2018, amifampridine phosphate (Fridapse) was approved for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults.
    National Library of Medicine Drug Information Portal


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Organizations Providing General Support

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

        In-Depth Information

        • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Lambert Eaton myasthenic syndrome. Click on the link to view a sample search on this topic.


          1. NINDS Lambert-Eaton Myasthenic Syndrome Information Page. Institute of Neurological Disorders and Stroke (NINDS). https://www.ninds.nih.gov/Disorders/All-Disorders/Lambert-Eaton-Myasthenic-Syndrome-Information-Page#disorders-r1. Accessed 12/22/2016.
          2. Stickler, DE. Lambert-Eaton Myasthenic Syndrome. Medscape. May 06, 2016; https://emedicine.medscape.com/article/1170810-overview.
          3. Lambert-Eaton Syndrome. MedlinePlus. 5/30/2016; https://www.nlm.nih.gov/medlineplus/ency/article/000710.htm.
          4. Titulaer, M. Lambert-Eaton myasthenic syndrome. Orphanet. November 2013; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=43393.
          5. Lambert-Eaton Myasthenic Syndrome (LES). Muscular Dystrophy Association (MDA). https://www.mda.org/disease/lambert-eaton-myasthenic-syndrome. Accessed 12/22/2016.
          6. Gozzard, P. Lambert-Eaton myasthenic syndrome. NORD. 2012; https://rarediseases.org/rare-diseases/lambert-eaton-myasthenic-syndrome/.

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