We present the case of a 33-year-old woman who within weeks developed severe swallowing difficulties and weakness in her limbs to an extent requiring hospitalization. Workup confirmed clinically suspected diagnoses of polymyositis and autoimmune myasthenia. A suspicion of malignant thymoma based on chest computed tomography was histologically verified. Patient treatment and response are presented. The case emphasizes the importance of recognizing that thymomas, in rare instances, may present with a combination of neuromuscular disorders in the same patient.