Case 8 -

Yersiniosis Laura W. Lamps, M.D. Audrey J. Lazenby, M.D. Joel K. Greenson, M.D.

Clinical Presentation: This case is a compilation of features from two patients. In the first case a 24 year old man presented with diarrhea and abdominal pain. The second case is that of a 50 year old man with abdominal pain and fever. Case 8 - Figure 1 - Note expansion of lamina propria by inflammatory infiltrate and mucosal edema at low magnification, yet preservation of architecture. Case 8 - Figure 2 - Higher magnification shows prominent neutrophils within the lamina propria, particularly within the upper half of the mucosa; there is also focal cryptitis. These features are typical of the "acute self-limited colitis" pattern of inflammation. Case 8 - Figure 3 - Marked lymphoid hyperplasia and epithelioid granulomas with giant cells are seen in this right colon section. Case 8 - Figure 4 - Higher magnification shows cryptitis, crypt abscesses, and mild architectural distortion. Endoscopic Findings: In the first case, the endoscopist saw a friable, nodular mass in the ileocecum. In the second case, the endoscopist saw patchy areas of ulceration and mucosal nodularity in the ileum and right colon, with intervening areas of normal mucosa. Diagnosis : Yersinia infection General Comments: Yersinia is one of the most common causes of bacterial enteritis in Western and Northern Europe, and numerous cases have been documented in North America and Australia Y. enterocolitica (YE) and Y. pseudotuberculosis (YP) are the two Yersinia species pertinent to human gastrointestinal disease. The reported incidence of Yersinia infection is rising rapidly within both Europe and the United States. These Gram-negative coccobacilli are causative agents in appendicitis (primarily granulomatous), ileitis, colitis, and mesenteric lymphadenitis. Infection with either species may cause symptoms and signs of an acute abdomen, chronic abdominal pain, and diarrhea. Although yersiniosis is usually a self-limited process, chronic infections (including chronic colitis) and persistent abdominal pain have been well documented. Immunocompromised and debilitated patients, as well as patients on deferoxamine or with iron overload, are at particular risk of serious disease. Pathologic features: Yersinia preferentially involves the ileum, right colon, and appendix. It is responsible for many cases of isolated granulomatous appendicitis. Grossly, involved bowel has a thickened, edematous wall with nodular inflammatory masses centered around Peyer's patches. Apthoid and linear ulcers may be seen. Involved appendices are enlarged and mimic suppurative granulomatous appendicitis; perforation is often seen. Involved lymph nodes may show gross foci of necrosis. The inflammatory pattern in yersiniosis is variable. Both suppurative and granulomatous patterns of inflammation may be seen, and a mixture of the two is common. Infection with YE has not typically been associated with discrete granulomas, but has been characterized hyperplastic Peyer's patches with overlying ulceration and accompanying acute inflammation, hemorrhagic necrosis, and palisading histiocytes . Gastrointestinal infection with YP has characteristically been described as a granulomatous process with central microabscesses, almost always accompanied by mesenteric adenopathy. Recent studies have shown that there is significant overlap between the histological features of YE and YP infection, and that either species may show lymphoid hyperplasia, epithelioid granulomas with prominent lymphoid cuffing, transmural lymphoid aggregates, giant cells, mucosal ulceration, cryptitis, and concomitant lymph node involvement. Some patients show only an "acute self-limited/infectious colitis" type pattern. Special stains are often not helpful in the diagnosis of Yersinia, for the organisms are small, may be present in low numbers, and are difficult to distinguish from normal nonpathogenic colonic flora. Cultures, serologic studies, and PCR assays may be helpful in confirming the diagnosis. Pathogenesis: Yersinia is harbored in meats, poultry, milk, eggs, and water, and colonizes many domestic pets and farm animals. Pathogenic Yersinia strains are thought to invade the mucosa of the intestine and multiply within Peyer's patches and the regional nodes to which they drain. Further spread is hematogenous. It is postulated that in some patients organisms can survive for extended periods of time within Peyer's patches, leading to chronic yersiniosis. Differential diagnosis: The major differential diagnoses include other infectious processes, particularly Mycobacteria and Salmonella. Acid fast stains and culture results should help to distinguish mycobacterial infection; clinical features and the presence of greater numbers of neutrophils, microabscesses, and granulomas may help to distinguish yersiniosis from salmonellosis. Crohn's disease and yersiniosis may be very difficult to distinguish from one another, and it is very important to keep this entity in the differential diagnosis of Crohn's disease as it is usually a self limited process with no further sequelae for the patient. Both Crohn's and yersiniosis may show very similar histologic features, including transmural lymphoid aggregates, skip lesions, and fissuring ulcers. In fact, isolated granulomatous appendicitis has in the past frequently been interpreted as primary Crohn's disease of the appendix However, patients with granulomatous inflammation confined to the appendix rarely develop generalized inflammatory bowel disease. Features that may favor Crohn's include cobblestoning of mucosa and creeping fat grossly, and changes of chronicity microscopically including crypt distortion, thickening of the muscularis mucosa, and prominent neural hyperplasia. However, some cases are indistinguishable on histologic grounds. Treatment: Most infections are either self-limited or resolve with a course of antibiotics. Debilitated patients, or those in whom the infection has disseminated, could require intensive supportive care and IV antibiotics. References: Gleason TH, Patterson SD. The pathology of Yersinia enterocolitica ileocolitis. Am J Surg Pathol 6:347-355, 1982. El-Maraghi NRH, Mair N. The histopathology of enteric infection with Yersinia pseudotuberculosis. Am J Clin Pathol 71:631-639, 1979. Lamps LW, Madhusudhan KT, Greenson JK, et al. The role of Y. enterocolitica and Y. pseudotuberculosis in granulomatous appendicitis: a histologic and molecular study. Am J Surg Path 25:508-15, 2001. Dudley TH, Dean PJ. 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