Malignant thymoma with metastasis associated with paraneoplastic myasthenia gravis.

We describe a patient who initially presented with a mixed thymic tumor and developed myasthenia gravis 8 years following thymectomy with recurrence of metastatic disease. Metastasis to the pleura, mediastinum, and cervical spine was identified with a positron emission tomography scan when this patient presented with recurring pneumonias and atrial fibrillation. The presentation and diagnosis were clouded by multiple courses of prednisone and chemotherapy for respiratory complications and metastatic disease, respectively. Classical myasthenia gravis symptoms emerged when his prednisone was tapered. The delayed presentation of paraneoplastic disease and the rare metastatic site make this case particularly unusual.