Myasthenia gravis with a paraneoplastic marker.

Ocular manifestations of myasthenia gravis are very common. Myasthenia gravis may be associated with lung carcinoma. Lambert-Eaton syndrome is also commonly associated with lung carcinoma and can have ocular manifestations. Overlap of these two entities has been described. The case of a patient with fatigable diplopia and ptosis 3 years after removal of a large-cell lung carcinoma is presented. Tests results for acetylcholine receptor binding and modulating antibodies were positive for myasthenia gravis. Test results for presynaptic voltage-gated calcium channel antibodies of the N-type were also positive. However, test results for the P/Q-type voltage-gated calcium channel antibodies, which are consistent with Lambert-Eaton syndrome, were negative. Autoantibodies can be used to serologically distinguish paraneoplastic myasthenia gravis from Lambert-Eaton syndrome.