EP238 - Perianal Tuberculosis – The Great Mimicker

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Purpose/Background: Perianal tuberculosis is a rare form of extra-pulmonary tuberculosis with limited cases described in literature. Its presentation typically includes non-healing perianal ulcers, recurrent fistula-in-ano, anal strictures and inguinal lymphadenopathy. Rarely, it can present as an anal mass that is clinically indistinguishable from an anal carcinoma. Accurate diagnosis is paramount as it avoids subjecting patients to ineffective treatments and reduces unnecessary surgical procedures.

Methods/Interventions: A 67-year-old Chinese gentleman with a 50-pack year smoking history and no past medical history presented to the emergency department with fecal incontinence and perianal pain for six months. He also reported constitutional symptoms of lethargy, loss of appetite and loss of weight. On examination, he had a fungating anal mass at six o’clock extending into the distal rectum and lax anal sphincter tone. Biochemical investigations were normal. MRI scan done noted likely T3N2M1 anal carcinoma with para-aortic and bilateral inguinal nodal metastasis. Colonoscopy performed noted anorectal mass. Multiple biopsies were taken and returned as inflammation and ulceration without evidence of neoplasia. Ziehl-Neelsen stain returned positive for acid fast bacilli. Acid fast bacilli cultures confirmed presence of Mycobacterium tuberculosis complex. He was promptly referred to infectious diseases physicians and started on anti-tuberculosis therapy. Interval follow-up in two weeks after starting anti-tuberculosis therapy revealed that the anal mass has shrunken in size with complete resolution of incontinence.

Results/Outcomes: It might be challenging differentiating between anal carcinoma and perianal tuberculosis as they share several common features from symptoms to macroscopic appearance. Microscopic appearance becomes even more important in this situations. Ziehl-Neelsen staining and cultures assist with confirming diagnosis. Literature review done noted that there are less than 70 cases of perianal tuberculosis described. Of which, there are only two cases where the patients presented with an anal mass. With the rise of tuberculosis cases globally, clinicians should be cognizant and consider perianal tuberculosis as a differential for anal mass.

Conclusion/Discussion: This case report highlights the diagnostic challenges of an anal mass and the importance of early recognition of perianal tuberculosis to prevent recurrences and unnecessary surgical interventions in patients. As seen in this case report, prompt initiation of anti-tuberculosis therapy yields favorable outcome.