An Unusual Case of Abdominal Actinomycosis Mimicking Inflammatory Bowel Disease

Abstract

Purpose: Introduction: Actinomycosis (AMC) is a chronic granulomatous disease manifesting in a number of ways, including fistula, sinus, mass or abscess. This disease very typically subscribes to an indolent course with non-specific signs and symptoms, often leading to delayed diagnosis. Abdominal AMC accounts for only approximately 20% of clinical presentations, with the majority of cases localized to the cervical and thoracic regions. However, within this 20%, the appendiceal site is by far the most common. AMC is sensitive to penicillin, and adequate treatment will almost always result in a full and permanent recovery. Case Presentation: A 23-year-old male without significant prior medical history who was referred to gastroenterology for evaluation of suspected Crohn's Disease. The patient endorsed progressively worsening abdominal pain, diarrhea and hematochezia of one month duration and had undergone abdominal imaging with an abdominal CT revealing diffuse thickening of the distal ileum with dilation of the proximal small bowel, suggestive of “ileitis secondary to Crohn's disease.” Prior to gastroenterologic evaluation, the patient developed acute small bowel obstruction with perforation and feculent pelvic peritonitis. He underwent emergent surgery requiring ileocectomy, appendectomy and resection of approximately 27 cm of distal ileum. The resected portion of bowel demonstrated chronic and focal active ileitis with architectural disarray and rare noncaseating submucosal granulomas in the appendiceal portion with focal ulceration. The patient was treated with intravenous steroids, which seemingly worsened his condition. Culture of the resected bowel subsequently grew Actinomyces israelii, at which time the patient was placed on intravenous clindamycin, given his anaphylactic allergy to penicillin. Patient noted marked improvement of his symptoms. Inflammatory markers returned to normal. He completed therapy with a 12 month course of oral doxycycline, and continues to remain asymptomatic without further complication. Repeat colonoscopy with multiple biopsies revealed no evidence of crypt architectural distortion, granuloma or dysplasia to indicate IBD. Discussion: Abdominal AMC is an exceedingly rare cause of abdominal pain in males, with only a few known case reports. However, given its propensity to form abscess and fistulize, it should be considered in the differential for all patients presenting in this manner, particularly if imaging localizes abnormalities to the distal ileum and appendiceal area. Early recognition of this process may prevent extensive surgical procedures and expensive, ineffective therapies.