LEMS (zero to finals)

Question 1

What is LEMS?

Answer 1

An autoimmune condition affecting the neuromuscular junction, similar to myasthenia gravis.

Question 2

Generally, how do the symptoms of LEMS differ from myasthenia gravis?

Answer 2

The symptoms tend to be more insidious and less pronounced than myasthenia gravis.

Question 3

In many cases LEMS is a paraneoplastic syndrome, occurring as a result of what tumour type in the body?

Answer 3

Small cell lung cancer

Question 4

Does LEMS always occur with small cell lung cancer?

Answer 4

No

It can occur as a primary autoimmune disorder without the presence of SCLC.

Question 5

What is the underlying pathology of LEMS?

Answer 5

Lambert-Eaton myasthenic syndrome results from antibodies against voltage-gated calcium channels.

Question 6

What can be the cause of antibody production against voltage-gated calcium channels in LEMS?

Answer 6

These antibodies may be produced in response to small-cell lung cancer (SCLC) cells that express voltage-gated calcium channels.

They target and damage voltage-gated calcium channels in the presynaptic membrane of the neuromuscular junction.

Question 7

What is the role of the voltage gated calcium channels?

Answer 7

Voltage-gated calcium channels are responsible for assisting in the release of acetylcholine into the synapse of the neuromuscular junction.

Question 8

What are the key presenting features of LEMS?

Answer 8

Proximal muscle weakness, causing difficulty climbing stairs, standing from a seat or raising the arms overhead

Autonomic dysfunction, causing dry mouth, blurred vision, impotence and dizziness

Reduced or absent tendon reflexes

Question 9

Signs and symptoms of LEMS worsen after periods of muscle contraction. True/false?

Answer 9

False

Signs and symptoms improve after periods of muscle contraction, which is the reverse of what is seen in myasthenia gravis.

Question 10

What is the most essential part factor in managing LEMS?

Answer 10

Excluding underlying malignancy (i.e. small cell lung cancer) is essential.

Question 11

What is the main medication used for management of LEMS and what is it’s mechanism of action?

Answer 11

Amifampridine

This works by blocking voltage-gated potassium channels in the presynaptic membrane, which in turn prolongs the depolarisation of the cell membrane and assists calcium channels in carrying out their action.

Question 12

What are some other options for treating LEMS?

Answer 12

Pyridostigmine (cholinesterase inhibitor)

Immunosuppressants (e.g., prednisolone or azathioprine)

IV immunoglobulins

Plasmapheresis