Myasthenia gravis is not a frequent disease in the elderly. The diagnosis of this neuromuscular junction disease in the elderly is difficult because of comorbidities and the broad differential diagnosis. We report here the case of a 86-year-old woman referred to hospital for loss of weight and difficulties in feeding. She was cachectic and had been suffering from dysphagia for several weeks. One week later, her clinical state worsened with the appearance of ptosis and oropharyngeal dysfunction, disturbing eating and talking. Myasthenia gravis was suspected and confirmed by a positive acetylcholine receptor antibody titer. The clinical state of the patient unfortunately worsened, with acute respiratory insufficiency, causing death. Myasthenia gravis must be suspected in a context of dysphagia, swallowing difficulties and loss of weight. This diagnosis leads to specific and symptomatic treatment and allows neuromuscular blockade-inducing drugs to be avoided.