RESUMEN
The initial presentation of myasthenia gravis as trismus is very rare and no previous reports have been found in the literature. A 35-year-old male presented to the outpatient unit of our department with inability to clench well and to open his mouth. Physical examination revealed that he had clinical findings consistent with the signs and symptoms of myasthenia gravis. He was immediately referred to a neurologist, who confirmed that he was in an advanced stage of myasthenia gravis with severe deficit to his respiratory muscles and he was promptly treated. He is presently on a maintenance drug therapy. To our knowledge, this is the first reported case of myasthenia gravis whose initial presentation was trismus. This case presents a rare but important diagnosis that should be added to the differential diagnosis of trismus.