TY - JOUR T1 - Refractory <em>Mycobacterium genavense</em> infection secondary to thymoma-associated endogenous IL-12 inhibitor JF - BMJ Neurology Open JO - BMJ Neurol Open DO - 10.1136/bmjno-2022-000285 VL - 4 IS - 1 SP - e000285 AU - Jessie Chen AU - MaiAnh Nguyen AU - Hannah Hu AU - Elaine Cheong AU - D Sean Riminton AU - Stephen Reddel Y1 - 2022/05/01 UR - http://neurologyopen.bmj.com/content/4/1/e000285.abstract N2 - Case A 39-year-old man with thymoma-associated acetylcholine receptor antibody myasthenia gravis (MG) presented with fevers, night sweats, abdominal pain and weight loss. Marked splenomegaly and intra-abdominal lymphadenopathy were found. Biopsies confirmed disseminated Mycobacterium genavense infection. Despite antimicrobials and reduced immunosuppressive medications, he worsened. We suspected a thymoma-associated cytokine inhibitory antibody. The addition of subcutaneous interferon-gamma (IFN-γ) induced clinical and radiological improvement. His antimicrobials were able to be ceased. MG remained stable. Subsequent testing demonstrated an endogenous interleukin-12 (IL-12) inhibitor, likely inhibiting the IL-12/IFN-γ axis crucial for defence against mycobacterial infections.Discussion This case illustrates the autoimmune manifestations that can occur with thymoma. It illustrates the benefit of exogenous IFN-γ in overcoming the immune deficit. In this case, its use did not exacerbate existing autoimmune disease or trigger others. We raise awareness of the need to consider cytokine pathway defects as a contributing factor to refractory atypical infections in patients with thymoma-associated MG.Data are available upon reasonable request. ER -