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Eaton-Lambert syndrome

Last edited: 4/16/2026

Overview

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder characterized by proximal muscle weakness, reduced muscle reflexes, and often dry mouth, frequently associated with small-cell lung cancer 1.

Diagnosis

  • Clinical Presentation: Proximal muscle weakness, reduced or absent muscle stretch reflexes, dry mouth 1.
  • Electromyography (EMG): Low-amplitude muscle responses with post-activation facilitation 1.
  • Serology: Presence of circulating antibodies to voltage-gated calcium channels 1.
  • Malignancy Screening: Essential, particularly in older patients with smoking history 1.

    • Management

  • First-Line Treatment: 3,4-Diaminopyridine (DAP) for over 85% of patients, with marked improvement in over half 1.
  • Cancer Treatment: Successful treatment of underlying malignancy often improves LEMS symptoms 1.
  • Adjunctive Therapies: Immunosuppressive agents (e.g., prednisone, IVIG) may be considered for refractory cases, though specific dosing is not detailed 1.

    • Special Populations

  • Malignancy Association: Older patients with smoking history have higher risk of associated malignancies 1.
  • Autoimmune Context: Younger, nonsmoking patients may have LEMS as part of broader autoimmune conditions 1.

    • Key Recommendations

  • High Index of Suspicion for Malignancy: Screen for malignancy, especially in older smokers, upon diagnosis of LEMS (Evidence: Strong 1).
  • Use of 3,4-Diaminopyridine (DAP): Initiate DAP for symptomatic relief in LEMS patients (Evidence: Strong 1).
  • Evaluate for Underlying Cancer: Intensive search for malignancy is crucial in older patients with LEMS (Evidence: Strong 1).

    • References

    1 Sanders DB. Lambert-eaton myasthenic syndrome: diagnosis and treatment. Annals of the New York Academy of Sciences 2003. link

    Original source

    1. [1]
      Lambert-eaton myasthenic syndrome: diagnosis and treatment. — Sanders DB Annals of the New York Academy of Sciences (2003)
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