Lambert-Eaton myasthenic syndrome - Recent developments, diagnostic methods and case report of a patient with concomitant myasthenia gravis

The Lambert Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of peripheral presynaptic acetylcholine (ACh) release resulting in muscle weakness and autonomic dysfunction. There is a very high coincidence with some neoplasms, particularly small cell lung carcinoma, therefore a thorough investigation is essential, and some new approaches (e.g. determination of anti-Hu antibodies) could help in this search. The ACh release abnormality is a consequence of an antibody attack on presynaptic voltage-gated calcium channels, the P/Q type of channel playing the most important role, Disease manifestation just by neuromuscular land neuroglandular) dysfunction, in spite of the distribution of the same channel types on many neuronal and non-neuronal cells, possibly results from a specific cluster organization of these channels in the neuromuscular junction, 'amplifying' thus the disabling effect of antibodies. The antibodies probably act by cross linking the channels, rather than directly binding their functional sites. The role of antibodies against other neuromuscular structures is still discussed. Currently, the diagnosis of LEMS is based on clinical and EMG (particularly stimulation-EMG) findings, Nevertheless, recent immunoprecipitation techniques enabling determination of anti bodies against the P/Q type of voltage-gated calcium channels represent a new promising diagnostic tool. Current treatment of LEMS comprises plasmapheresis, prednisone, azathioprine. Of course, antitumour therapy is essential in paraneoplastic cases. As an asymptomatic therapy 3,4-diaminopyridine is administered. More aggressive immunosuppressants have also been used. In the case report we describe a case of a young female patient with a 16-year course of both LEMS and myasthenia gravis without any known malignancy. The above mentioned immunoprecipitation test was also positive in the patient.