What is the epidemiology of Lambert-Eaton myasthenic syndrome (LEMS) in the US?

Updated: May 23, 2019
  • Author: David E Stickler, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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The true incidence of LEMS is unknown. An estimated 3% of patients with SCLC have LEMS. The prevalence of SCLC is 5 cases per million population in the United States. Because only 50-70% of patients with LEMS have an identifiable cancer and because LEMS goes undiagnosed in many patients, the true total prevalence of LEMS may be considerably higher.

The overwhelming majority of cancers associated with LEMS are SCLC. However, many different malignancies may be involved. A partial list includes non-SCLC; neuroendocrine carcinomas; lymphosarcoma; malignant thymoma; cancers of the breast, stomach, colon, prostate, bladder, kidney, gallbladder, and rectum; basal cell carcinoma; leukemia; lymphoproliferative disorders such as Castleman syndrome; and Hodgkin lymphoma.

According to one estimate, there are approximately 400 cases in the United States at any given time. However, this estimate does not take into account the number of patients with LEMS who do not have SCLC or any other identifiable malignancy.

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