Diagnosing LEMS

Early recognition of LEMS symptoms can lead to quicker diagnosis and initiation of effective treatment12

Common LEMS Symptoms12

Anatomical display of neuromuscular and autonomic symptoms of LEMS
Anatomical display of neuromuscular and autonomic symptoms of LEMS


All of the following are characteristic symptoms of LEMS except:


Weight loss/loss of appetite is not a characteristic symptom of LEMS. The disease is characterized by proximal muscle weakness, autonomic symptoms, and hyporeflexia or areflexia.12

Proximal leg and hip girdle weakness can create a specific LEMS gait

LEMS typically starts with muscle weakness in the upper legs and hips, including the pelvic girdle.12 As symptoms spread and worsen, the patient’s gait is affected, making walking difficult and unsteady.5,6 In some cases, this weakness leads to a specific waddling motion, commonly referred to as “LEMS gait.”

Proximal weakness in LEMS video thumbnail

Proximal Weakness in LEMS

In this short video, you will see a demonstration of the classic deficits of a person with proximal weakness due to LEMS. The patient’s use of an assisted walking device, difficulty walking, and trouble getting up from a chair all display examples of proximal weakness.

Diagnostic methods

If you suspect that your patient may have LEMS, you can utilize several clinical diagnostic methods to get them on the right treatment path.12


A diagnosis of LEMS may be suspected based on clinical symptomatology and physical signs, including proximal muscle weakness, autonomic dysfunction, and hyporeflexia or areflexia. However, a definitive diagnosis should be made only after confirmatory testing using the test methods below.12


Anti-VGCC antibody testing
These antibodies are found in 85%-90% of LEMS patients.12

  • The presence of anti-VGCC antibodies can support a LEMS diagnosis, although it should be noted that a negative antibody test does not rule out a diagnosis of LEMS21
  • Electrodiagnostic testing should be performed as a follow-up21

Electrodiagnostic testing
Increment on high-frequency repetitive nerve stimulation or post-exercise potentiation can also confirm diagnosis.12

  • Consider testing patients who have symptoms of MG, especially with low compound muscle action potential (CMAP) amplitudes on regular nerve conduction studies12

Free LEMS diagnostic test available

Did you know that Catalyst offers a no-cost test that can identify the presence of VGCC antibodies in suspected LEMS patients?

Uncovering hidden cancer: another benefit of early recognition and diagnosis of LEMS5,12

The sooner LEMS is identified as the disorder behind your patients’ symptoms, the sooner treatment can begin. Treatment for LEMS will be predicated on how the disorder is manifested.16

Manifestations of LEMS

LEMS can manifest in association with an underlying cancer16 or in the absence of an underlying cancer.12,22


  • Most commonly associated with SCLC; however, it is possible that LEMS may occur with other cancers16,23
  • Predominantly affects males 60 or older, many with a history of smoking22
  • Symptom onset is variable, ranging from 6 years prior to cancer diagnosis to 5 years after cancer diagnosis16*
  • Patients with LEMS associated with SCLC display a more rapidly progressing course of disease vs those with LEMS not associated with SCLC14,15


  • Increased occurrence with other autoimmune disorders22
  • Typical age of onset is 35-40; gender-neutral12,22
  • Slower progression/fluctuating symptoms12
  • The average life expectancy is similar to that of a healthy individual of the same gender and a similar age24
*Results from a study involving 133 patients with cancer-associated LEMS.

LEMS Pop Quiz

LEMS is most often associated with which type of cancer? (please select one)


Although LEMS occurs with several different cancer types, it is most often associated with small cell lung cancer.16,21