We present the case of a 50-year-old male diagnosed with myasthenia gravis, secondary to thymoma or Lambert-Eaton syndrome during the study of repeated vomiting. Gastrointestinal symptoms persisted despite the treatment of the thymoma. He suffered from sigma volvulus that required sigmoidectomy 9 years after diagnosis. Neuromuscular junction disorders are not characterized by gastrointestinal involvement, as in our case. They have previously sporadically been related to intestinal motility dysfunction.