What is the relationship between cancer and Lambert-Eaton myasthenic syndrome (LEMS)?

Updated: May 23, 2019
  • Author: David E Stickler, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Cancer is present or subsequently discovered in 50-70% of patients with LEMS. In the case of lung cancer, the clinical symptoms of LEMS may precede detection of the underlying disease. Symptoms of the underlying cancer, as well as the “B” symptoms of cancer, may be present.

Smoking and age at onset are major risk factors for cancer in patients with LEMS. Duration of symptoms is also a factor. If a tumor is not found within the first 2 years after symptom onset, cancer is unlikely. For example, a patient younger than 50 years at onset who does not have a tumor discovered after 2 years of close follow-up is unlikely to have an underlying cancer. On the other hand, a long-term smoker with LEMS onset after age 50 years probably has underlying lung cancer.

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