Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune condition in which antibodies attack the nerve endings and stop muscles from contracting, which causes muscle fatigue. For half of the people affected, LEMS is often an early sign of lung cancer as the condition is a unusual reaction against cancerous cells.

The difference between LEMS and myasthenia gravis (MG)

LEMS is a rare disorder of the nervous system caused by a disruption of how the nerve and muscle talk to each other. The disruptions are caused when antibodies bind to and attacks the nervous system. The reasons why this happens is currently unknown. This is very similar to myasthenia gravis, however the target of the attack is different in MG as the acetylcholine receptor on the nerve is affected, whereas in LEMS it's the voltage-gated calcium channel on the nerve.

Symptoms

Unlike myasthenia gravis, LEMS symptoms often start in the limbs. The legs will often feel heavy, a sensation described as ‘walking through treacle’. It can also affect the arms and is a lot less common for it to affect the facial muscles. Some people may also find that they experience problems with automatic bodily functions, dry mouth, constipation and impotence in men.

Diagnosis

To diagnose LEMS blood tests are used to detect the antibodies that cause the disease. In addition to this a test to assess muscle activity may also be offered. In addition to this, tests may also carried out for lung cancer. If no cancer is found, regular precautionary tests is advised.

Treatment

Pyridostigmine (Mestinon®)

Some people control their myasthenia with pyridostigmine alone, which temporarily improves nerve-muscle transmission to help muscle strength. The medication boosts the message from the nerve to the muscle resulting in easier muscle contraction and movement. It has to be taken periodically throughout the day for it to take full effect.

More information about pyridostigmine can be found on its designated information sheet.

3,4-Diaminopyridine (3,4-DAP)

3,4-DAP improves muscles transmission which helps to improve muscle strength by acting on the nerves to allow more of the chemical that stimulates muscle movement to be released. It starts to take effect within 60 minutes and is taken at the time when you need it most.

For more information, see its designated information sheet.

Prednisolone

This is a steroid that is often prescribed for myasthenia (typically on alternate days). Steroids reduced the production of antibodies by "damping down" the bodies immune system. Prednisolone is often started on a relatively high dose and gradually reduced until the optimum dosage is achieved. Symptoms usually start to improve 2-4 weeks after treatment is started. Maximum benefit is usually seen after 6-12 months of treatment.

More information can be found on its designated information sheet.

Azathioprine (Imuran®)

Azathioprine helps to reduce or suppress your body's own immune defense system. It acts slowly and can take up to a year to take full effect. Azathioprine can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Methotrexate

Methotrexate helps to reduce or suppress your body's own immune defense system. It can take up to 8-12 weeks to take full effect. Methotrexate can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Mycophenolate

Mycophenolate helps to reduce or suppress your body's own immune defense system. It can take up to 3-6 months to take full effect. Mycophenolate can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Ciclosporin

Ciclosporin helps to reduce or suppress your body's own immune defense system. It can take up to 2-3 months to take full effect. Ciclosporin can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.