[A case of Isaacs' syndrome preceding the recurrence of malignant thymoma--generating site of ectopic activity and therapy].

We described a-44-year old male patient with Isaacs' syndrome occurring 8 months before the recurrence of malignant thymoma. Electrophysiological examination suggested that spontaneous muscle activities were generated at the distal terminals of the motor nerves. Double filtration plasmapheresis alleviated the symptoms of neuromyotonia for a short term. Administration of valproic acid had more prolonged effects lasting for 2 months until his death from relapsed thymoma. Our results support that autoimmune mechanisms, especially humoral factors, are playing an important role in the pathogenesis of Isaacs' syndrome and that anti-convulsants therapy is important.