[Lambert-Eaton Myasthenic Syndrome].

Area of Science:

• Neurology
• Immunology
• Oncology

Background:

• Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder affecting neuromuscular junctions.
• It presents with proximal muscle weakness, reduced reflexes, and autonomic dysfunction.
• Prevalence is approximately 0.25-0.27 per 100,000 population.

Purpose of the Study:

• To summarize diagnostic criteria and treatment strategies for Lambert-Eaton myasthenic syndrome.
• To highlight the association between LEMS and small-cell lung carcinoma (SCLC).
• To provide an overview of current clinical practice guidelines for LEMS management.

Main Methods:

• Review of diagnostic criteria, including Japanese LEMS diagnostic criteria 2022.
• Analysis of pathogenic autoantibodies, particularly P/Q-type voltage-gated calcium channel (VGCC) antibodies.
• Examination of treatment modalities: oncological, immunotherapeutic, and symptomatic.

Main Results:

• Muscle weakness in LEMS is caused by autoantibodies against presynaptic VGCCs.
• A significant percentage (50-60%) of LEMS patients have an associated SCLC.
• P/Q-type VGCC antibody positivity is a strong diagnostic indicator.
• 3,4-diaminopyridine is effective for symptomatic treatment in most patients.

Conclusions:

• Accurate LEMS diagnosis relies on electrophysiological findings and myasthenic symptoms.
• Effective tumor treatment can improve LEMS symptoms in SCLC patients.
• Established treatment algorithms guide LEMS management, incorporating oncological, immunotherapeutic, and symptomatic approaches.