Isaacs' syndrome successfully treated by immunoadsorption plasmapheresis

We report a 70‐year‐old woman with Isaacs' syndrome (acquired neuromyotonia) who showed a marked improvement after immunoadsorption plasmapheresis (IAP). She developed hyperhidrosis in her teens, and slowly progressive symptoms of neuromyotonia for over 50 years. An in vitro investigation of her serum with patch‐clamp technique suggested the presence of antibodies against potassium channels. She was treated with IAP, which brought disappearance of her symptoms. Though the symptoms started to recur in 3 weeks, moderate improvement has been maintained by immunosuppressive drug treatment.