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Lambert-Eaton myasthenic syndrome

Also called LEMS or Eaton-Lambert syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a rare condition where the immune system attacks the connection between nerves and muscles. This causes muscle weakness, usually starting in the legs and hips. In about half of people it is linked to a type of lung cancer, called small cell lung cancer, which may be found before or after LEMS.

Last updated Nov 9, 2026

What it is

Tests to look for cancer are an important part of diagnosis and follow-up.

Medicines that improve nerve signals, and treatments that calm the immune system, can help. Treating any cancer may also improve symptoms.

Common signs

  • Weakness in the legs and hips
  • Difficulty climbing stairs or getting up from a chair
  • Dry mouth
  • Drooping eyelids
  • Tiredness

How it is usually diagnosed

  • Blood test for antibodies
  • Nerve conduction studies and EMG
  • CT or PET-CT scan to look for cancer

Records worth keeping

Keeping these together makes each appointment easier, especially when you see a new doctor:

  • Antibody test results
  • Nerve test reports
  • Cancer screening scan reports
  • Neurology letters

Questions to ask your doctor

  • Has cancer been ruled out?
  • How often will I need scans?
  • Which treatments could help my strength?

When to get help right away

Call 112 or go to the nearest emergency department if you have:

  • Difficulty breathing or swallowing: call 112

This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.

Sources

Related conditions

Myasthenia gravisA rare long-term condition causing muscle weakness that gets worse with use and better with rest. Treatment usually controls it well.Lung cancerOne of the most common cancers, mainly caused by smoking. Found early, it can often be treated successfully.