P-NJ002. Myasthena gravis, a great ‘mimicker’ as an initial autoimmune presentation of diffused large B cell lymphoma: a case report

Abstract

Introduction . Myasthenia gravis (MG) belongs to a spectrum of autoimmune diseases mediated by antibodies to acetylcholine receptors (AChRs) or muscle specific tyrosine kinase (MuSK). About 10-15% of MG cases have concurrent thymoma. However, only few reported cases of MG had been associated with lymphoid malignancies. Results . We report a case of MG in association with non-germinal center Diffuse Large B cell lymphoma (DLBCL) in a 40 years old gentleman. He initially presented with MG in crisis with bulbar and respiratory involvement in 2015. He was given intravenous immunoglobulin, steroid and pyridostigmine. He improved, however, defaulted his follow-up. Three years later, he presented back with MG in crisis. AChR antibody was positive and CT thorax showed anterior mediastinal mass with differential of thymoma or teratoma. Intravenous immunoglobulin was administered, but he developed acute extensive myocardial infarction. Thus, he underwent plasma exchange and tracheostomy due to prolonged ventilation. He was discharged well with steroid, pyridostigmine and azathioprine. He presented back 6 months later due to upper airway obstruction. Direct laryngoscope revealed enlarged fungating mass. Biopsy from right tonsil showed non germinal center DLBCL. He, subsequently, developed overwhelming sepsis with multiorgan failure and succumbed to death. Discussion . There are more than one pathogenetic mechanism that underlie the association between MG and lymphoma. There are pathways and genes involved in uninhibited lymphocytic proliferation which could result in both autoimmunity and lymphoma. Alternatively, lymphoid malignancy occurring after longstanding MG might be that the lymphoid malignancy is the result of chronic MG. MG also occur with higher frequency in lymphomas with mediastinal involvement due to the close proximity of lymphoma to the thymocytes that express proteins with antigenic similarities to AChR leading to autoimmune reaction to the latter. Conclusion . The association between MG and lymphoma although rare, can occur especially in those with mediastinal involvement.