A Case of Paraneoplastic Myasthenia Gravis as the Initial Presentation in a Patient with Non-Hodgkin’s Lymphoma (P3.6-011)

Objective: n/a Background: The association between myasthenia gravis (MG) and thymoma is well-established, however, MG has been less frequently associated with other malignancies. We present a case of a B-cell non-hodgkin’s lymphoma presenting as a new diagnosis of MG. Design/Methods: n/a Results: A 68-year-old man presented with diplopia, dysphagia and ptosis after a knee replacement. He was given steroids for possible angioedema of the tongue without benefit. After four months of progressive symptoms, work-up revealed positive AChR antibodies consistent with MG. He started prednisone, pyridostigmine and azathioprine with temporary benefit. Five weeks later, he was admitted with an NSTEMI, new systolic heart failure, refractory atrial fibrillation with RVR, respiratory failure requiring intubation, MG exacerbation, pancytopenia, fevers and shock. CT chest/abdomen/pelvis revealed retroperitoneal lymphadenopathy, but no thymoma. MRI brain and spine showed a thoracic subcutaneous mass, with biopsy confirming benign fibroadipose tissue. On further history, he had an unintentional 40lb weight loss over six months and three weeks of night sweats. A serum paraneoplastic panel revealed high titers of striational antibodies. Peripheral flow cytometry was positive for monoclonal B-cell lymphoproliferative disorder. Bone marrow biopsy showed low grade B-cell lymphoma. He improved with medical management and five days of IVIg for MG. He was discharged home on prednisone and pyridostigmine with no further MG symptoms. Conclusions: MG has rarely been reported in patients with B-cell lymphoma, and even more rarely as a presenting symptom. Azathioprine use has been linked to lymphoma in some populations, usually with prolonged use. Although our patient’s B symptoms preceded his MG diagnosis, suggesting a more indolent lymphoma that likely predated his treatment with azathioprine, it is possible that azathioprine played a role in his acute worsening and hospitalization. Regardless, this case emphasizes the importance of screening for signs or symptoms of other malignancies in patients diagnosed with thymoma-negative MG. Disclosure: Dr. Cormier has nothing to disclose. Dr. Schaefer has nothing to disclose.