Kasten, Mary J.

ABSTRACT Background Mycobacterium genavense is a rare opportunistic non-tuberculous mycobacterium primarily reported in advanced human immunodeficiency virus infection. Case Summary A 70-year-old woman with systemic lupus erythematosus developed progressive abdominal pain, weight loss, and mesenteric lymphadenitis repeatedly responsive to corticosteroids. Endoscopic biopsies revealed abundant acid-fast bacilli, and molecular testing confirmed the presence of M. genavense . Treatment with azithromycin, ethambutol, and rifabutin led to gradual recovery. Conclusion Steroid-responsive mesenteric inflammation in immunocompromised patients should prompt evaluation for infection, including mycobacteria and other culture-negative microorganisms using molecular diagnostics. This case report highlights the importance of plasma microbial cell-free DNA assays in the identification of fastidious organisms, like M. genavense , and, in some cases, serial testing may be useful to monitor treatment response.