Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder affecting the neuromuscular junction, which is the connection between muscle and nerve cells.

How LEMS affects the body

LEMS primarily affects the voluntary muscles — the group of muscles in the body that can be moved at will. But the autonomic nervous system also may be mildly affected. The autonomic nervous system regulates involuntary processes (bodily functions individuals cannot control) such as heart rate, breathing, eye responses, digestion, urination, etc.

The primary symptom of LEMS is a weakness in the leg and arm muscles. This muscle weakness can affect walking and climbing. Patients also may experience frequent muscle pain and cramps. As the condition progresses, the shoulder muscles, throat muscles that support speech and swallowing, and muscles in the eyes also may be affected.

Other symptoms

In addition to muscle weakness, LEMS patients may exhibit a combination of several other symptoms, including:

  • Fatigue
  • Pain
  • Muscle stiffness
  • Weight loss
  • Tingling in the feet or hands
  • Breathing problems
  • Dizziness
  • Constipation
  • Dry mouth
  • Trouble speaking or swallowing
  • Poor reflexes
  • Reduced sweating
  • Vision problems, dry eyes, droopy eyelids
  • A temporary gain in muscle strength during the start of exercise which is significantly reduced as the exercise routine continues
  • Erectile dysfunction

Additional information

The rarity of the condition and its slow progression, as well as the gradual onset of its symptoms and their similarity to those of other neuromuscular conditions, can cause a significant delay in diagnosing it. However, as the condition progresses, symptoms may become more severe and substantially reduce patients’ quality of life.

It is important to consult with a doctor about signs and symptoms to aid LEMS diagnosis and begin early treatment to manage the condition.


Last updated July 17, 2019


Lambert-Eaton News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare providers with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.