Concurrent Graves disease thyrotoxicosis and myasthenia gravis: the treatment of the former may dangerously reveal the latter.

Autoimmune thyroxicosis and myasthenia gravis are often associated. In both diseases, clinical features may include neuromuscular weakness, making their distinction challenging. We report a patient with known Graves disease who presented with generalised fatigue, initially attributed solely to thyrotoxicosis, and who experienced severe respiratory failure linked to associated myasthenia gravis that was unmasked by medication used in the perioperative management of his thyroxicosis. Anaesthetists should always consider myasthenia gravis in cases of hyperthyroidism presenting with neuromuscular features.