Capecitabine-related neurotoxicity presenting as trismus

Capecitabine is an oral fluoropyrimidine used for cancer treatment. It is generally well tolerated. A patient who had previously received adjuvant 5-fluorouracil without neurotoxicity had a severe adverse reaction when later given capecitabine in the metastatic setting. She presented with the acute onset of neuromuscular symptoms, the most prominent being trismus but also including slurred speech, confusion, gait abnormalities, and ocular changes. Her symptoms completely resolved with discontinuation of capecitabine.