Brainstem lymphoma in a myasthenia gravis patient on azathioprine

Azathioprine is used for immunosuppression in myasthenia gravis (MG). We report a patient with seropositive MG who developed a brainstem lymphoma 4 years after being treated with azathioprine and review the literature on the occurrence of lymphoma in this patient population. An 82-year-old man with ocular MG who had been on azathioprine for 4 years developed subacute worsening of bulbar symptoms including diplopia, dysarthria and dysphagia mimicking MG exacerbation. Neuroimaging followed by biopsy showed brainstem diffuse large B-cell lymphoma (DLBCL). To our knowledge this is the first reported patient with brainstem DLBCL after azathioprine treatment in MG. Lymphoma has been reported in MG patients treated with azathioprine, although the incidence is unknown. We suggest reduction of azathioprine dose and subsequent discontinuation, if possible, in MG patients who are in remission. Special caution should be taken with elderly patients and Epstein-Barr virus serology prior to initiation may be useful in this population, but this requires further study.