[Nicotine and worsening myasthenia].

We report a case of myasthenia gravis worsened by a nicotine transdermal system, in a man who usually was smoking fourty cigarettes per day without any worsening of his symptomatology. He noted an increased bilateral ptosis, total ophtalmoplegia, difficulty in chewing and generalized weakness two hours after application of a nicotine transdermal system, the symptoms improving after he removed it. Cholinergic receptors involved in myasthenia gravis are nicotinergic, and their number at the neuromuscular junction is reduced in myasthenia gravis. That leads to a "functional overdosage" after application of the nicotine transdermal system similar to the cholinergic crisis. This case can be compared with myasthenia syndromes described during the Second World War in tobacco chewers without any muscle impairment.