Eribulin Mesylate-related Multifocal Demyelinating Neuropathy with Myokymia in a Breast Cancer Patient.

We herein report a 48-year-old woman receiving eribulin mesylate for breast cancer who presented with gait disorder, distal limb paresthesia, and weakness progressing monthly. A nerve conduction study indicated demyelination with multifocal conduction block. Considering the immune-mediated pathology of her condition, she was administered intravenous immunoglobulin. Her neurological symptoms improved promptly after intravenous immunoglobulin therapy and eribulin withdrawal. Furthermore, the limb myokymia seen at the time of admission disappeared. Her symptoms continued to improve without additional treatment. We conclude that eribulin was a rare cause of demyelinating neuropathy with multifocal conduction block derived from immune-mediated pathology.