Overlooked Myasthenia Gravis in an Elderly Adult

To the Editor: Although myasthenia gravis (MG) may begin at any age, it can be overlooked in elderly adults, and the diagnosis is often delayed in elderly adults. One reason is the tendency to attribute the symptoms to more common diagnoses such as cerebrovascular disease. This letter discusses an individual with recurrent dysarthria, dysphagia, and a choking cough after drinking in whom the diagnosis of MG was overlooked. An 84-year-old man presented to the local hospital with dysarthria, dysphagia, and a choking cough after drinking. Magnetic resonance imaging of the brain showed multiple infarctions but no acute ischemic change. He was diagnosed with a cerebral infarction, and therapy was administered. His symptoms were relieved but became worse 1 month later, at which point he was sent to the local hospital again; homologue therapy was applied but did not work, and he was sent to Chinese PLA General Hospital for further therapy. His medical history was relevant for hypertension, chronic hepatitis C, villiform tubular adenoma of the colon, mushroom type tubular adenocarcinoma of the colon, and epidermal cancer of the bladder and urinary tract. On physical examination, he had mild dysarthria and left ptosis (said to be due to surgery to remove a cataract) with mild abnormal up-and-down extraocular movements of the left eye but no apparent diplopia. There was slight facial weakness on the left side but normal jaw strength. Motor testing of the four limbs and trunk revealed normal strength for an elderly man who can walk independently with the help of a cane. Sensation to pin prick was normal. The deep tendon reflexes were normal (++) and symmetric. Babinski sign was positive bilaterally. Findings from the rest of the neurological examination were unremarkable. Standard biological data were unremarkable. Hypertension was well controlled, and thyroid levels were normal. Brain magnetic resonance imaging showed multiple infarctions. During his hospitalization, swallowing function rehabilitation exercise was performed, and the choking cough after drinking improved, but he developed fatigue of the masseter muscle. His son revealed the undulatory property of his dysarthria and that his left ptosis had existed before the surgery on his eye. His ptosis and dysarthria were generally better in the morning and worse in the afternoon. He was admitted to the hospital because of dysarthria and dysphagia, but magnetic resonance imaging of the brain showed no acute ischemic change, and the brain lesions could not explain his left ptosis (Figure 1). Thus, MG was suspected, and the diagnosis was eventually confirmed by decrement on 3-Hz bilateral facial repetitive nerve stimulation and no increment on 20-Hz bilateral facial repetitive nerve stimulation. A chest scan showed no evidence of a thymoma. He was started on oral pyridostigmine bromide therapy. Intravenous immunoglobulin therapy was refused because of economic burden. Prednisone was not given in consideration of his age and cancer history. Within 3 days of therapy, he reported improvement in the fatigue of the masseter muscle, but his ptosis had not resolved. He could chew peanuts, which had been too difficult for him before therapy.