Subclinical myasthenia gravis causing increased sensitivity to botulinum toxin therapy.

In rare patients receiving botulinum toxin (BT) therapy the potency of the BT drug may be increased by pre-existent impairment of neuromuscular transmission (INT). Appropriate dose adjustment may correct for this. Subclinical INT has previously been described by us for the first time in a patient with Lambert-Eaton myasthenic syndrome. We are now describing subclinical INT for the first time in a patient with ocular myasthenia gravis. Due to its unpredictability subclinical INT may pose a risk to patients receiving BT therapy.