Figure 1



This figure illustrates the muscles of the body which are most often affected by LEMS.  The dark red colour indicates the muscle groups most often affected, the light red muscles less often affected and the pink areas indicate muscles which can be affected less commonly. 


The Symptoms of LEMS

The onset of LEMS is gradual and symptoms start with slowly progressive muscle weakness and fatigue; muscle aches and cramps are also frequent. The weakness commonly involves muscles of the hips and legs on both sides at the same time and can sometimes cause significant impairment of activities of daily living.

In contrast to Myasthenia-Gravis (MG), eye muscle impairment is rarely seen. Respiratory symptoms are also rare, but have been reported and shoulder muscles are less affected.

In patients with LEMS involuntary muscles can also be affected; these symptoms include dry mouth with metallic taste, constipation or erectile dysfunction.

 




Table 1: 
Comparing LEMS with Myasthenia-Gravis







"Living with Lambert-
Eaton Myasthenic Syndrome"
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Lambert Eaton Myasthenic Syndrome (LEMS) is an autoimmune neuromuscular disorder affecting the presynaptic neuromuscular junction.



LEMS is considered to be a rare autoimmune disease with the primary symptoms of muscle weakness. Muscle weakness in LEMS is caused by auto-antibodies to voltage gated calcium channels at the presynaptic side of the neuromuscular junction leading to a reduction in the amount of acetylcholine released from nerve terminals (See Diagrams on What Causes LEMS? page.)
Patients with LEMS typically present with fatigue, muscle pain and stiffness. The weakness is generally more marked in the lower extremity muscles, particularly of the legs and hip-girdle. See Figure 1
Other problems include reduced reflexes, drooping of the eyelids, facial weakness and problems with swallowing. Patients often report a dry mouth, impotence, and constipation.



Very rarely these problems can be life-threatening when the weakness involves respiratory muscles.

A diagnosis of LEMS is generally made on the basis of clinical symptoms, electromyographic (EMG) testing and the presence of auto-antibodies against voltage gated calcium channels.



LEMS is usually associated with an underlying disease; a cancer in about half of patients, the majority of whom have a "small cell" lung cancer (SCLC). In the remaining cases no cause is found and the disease is called non-paraneoplastic Lambert-Eaton Myasthenic Syndrome.


The diagnosis of LEMS may be missed or delayed. Patients may have had symptoms for many months before a LEMS diagnosis is made.
The main symptom of LEMS is muscle weakness, therefore patients typically have difficulty rising from a chair, climbing stairs and walking.



The neck and eye muscles are affected in about one quarter of cases of LEMS with symptoms including drooping eyelids, dry mouth, blurred vision and difficulty swallowing but usually not to the same extent or severity as found in Myasthenia-Gravis which is another neuromuscular disease. Differentiation between the two diseases may be difficult.
Initial strength improvement after exercise is common in LEMS. This also can occur in patients with Myasthenia-Gravis. However, repeated testing of many separate muscle groups may differentiate the two diseases. Many patients have some degree of autonomic dysfunction, usually characterised by dry mouth. This may be the initial presenting symptom.


Myasthenia-Gravis is similar to LEMS and Congenital Myasthenic Syndrome. In all of these the main problem is painless weakness of voluntary muscle caused by disruptions in nerve to muscle impulses.
The most common is Myasthenia-Gravis, sometimes called MG.

LEMS is at least ten times less common than MG. Although muscle weakness is the main problem, it fluctuates less than in MG. Whereas MG particularly affects the eye, face, neck and chest movements, LEMS show a more bottom-up pattern, the legs feel heavy initially and upper body symptoms around the arms and face follow later. Very often there are also problems with ‘automatic’ bodily functions. See Table 1
Congenital Myasthenic Syndrome is an inherited disorder rather than an autoimmune disorder. It therefore mainly affects children and symptoms can include severe muscle weakness, feeding and respiratory problems, and delays in the ability to sit, crawl and walk. This is a rare condition.




LEMS is considered a neurologic disorder and it has two forms. As described above, about half of people have a cancer, the majority of whom have a "small cell" lung cancer (SCLC), which mainly happens in people who smoke. This LEMS usually starts after age 50. This form of LEMS is referred to as paraneoplastic.
In other people, there is no tumour and this type of LEMS usually starts after the age of 40 but it can start in children under the age of 10. This is called non-paraneoplastic LEMS.





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