Mycobacterium gordonae Infection Presenting as Appendiceal Mass

Abstract

Introduction: The nontuberculous mycobacteria (NTM) are recognized as occasional human pathogens. Mycobacterium gordonae is believed to be one of the least pathogenic of this class. We present a case of M gordonae infection presenting as an appendiceal mass. Methods: The patient is a 50-year-old man presenting with abdominal pain. An abdominal CT demonstrated a dilated appendix with adjacent fat stranding and reactive lymphadenopathy concerning for appendiceal malignancy vs acute appendicitis. Results: Histological examination revealed an appendix with acute inflammation, extensive granulomatous change, and significant granulomatous lymphoadenopathy. Some of the granulomata showed central necrosis and neutrophil aggregates. No features of malignancy were seen. An infectious etiology was favored. Extensive microbiology workup, including various cultures, serologies/titers, TB tests (AFB and Quantiferon), and 16s/18s ribosomal PCR, was performed. M gordonae DNA was detected via the PCR method. Discussion: Recognizing histopathological features of infectious granulomatous appendicitis is important for early therapy and improving patient care: tuberculosis shows characteristic caseation and necrotizing granulomas; Yersinia infections show cryptitis, necrotic stellate abscesses in bowel wall, deep and penetrating ulceration, epithelioid granulomas, and mesenteric lymph nodes with lymphoid and histiocytic hyperplasia; Mycobacterium avium-intracellulare usually involves immunocompromised/elderly patients, it expands the lamina propria with a lymphohistiocytic infiltrate, and mesenteric lymph nodes are usually not involved; and Bartonella henselae may show necrotizing granulomas in liver with neutrophils, but the appendix is usually not involved. For NTM lymphadenitis, routine biopsy or incisional drainage should be avoided. The treatment of choice is excision of involved nodes by an experienced surgeon. In our case, hemicolectomy with associated mesenteric lymph nodes was a curative treatment. Conclusion: M gordonae could be a rare clinically significant pathogen, not just specimen contaminants.