An 85-year-old man presented to hospital as an emergency having difficulties with swallowing and speech. In the emergency department, he was assessed as having acute onset dysphagia and dysarthria in keeping with an acute stroke. Subsequently, it became apparent that although the symptoms were indeed of relatively acute onset, there was a clear description by the patient of fatigability and diurnal variation, prompting a working clinical diagnosis of myasthenia gravis. The patient followed a turbulent clinical course, and interpretation of investigation results proved not to be straightforward in the acute setting. Myasthenia gravis is an uncommon disorder but it is more common in the elderly. This case provides key learning points, particularly highlighting the value of prompt, accurate clinical assessment and the importance of adhering to the clinical diagnostic formulation.