The role of Yersinia enterocolitica and Yersinin pseudotuberculosis in granulomatous appendicitis - A histologic and molecular study

Granulomatous appendicitis is an enigmatic entity. Purported causes include Crohn's disease, foreign body reactions, sarcoidosis, and infectious agent s; however, most cases remain idiopathic. Yersinia enterocolitica (YE) and Y. pseudotuberculosis (YP) have been implicated as causes of appendicitis, ileocolitis, and mesenteric adenitis. The authors examined the potential ro le of YE and YP in granulomatous appendicitis using histologic and molecula r methods. Forty cases of granulomatous appendicitis were evaluated for his tologic features including transmural inflammation; number and character of granulomas, and mucosal changes. Twort Gram, Grocott methenamine-silver (G MS), and Ziehl-Neelsen stains were evaluated, and polymerase chain reaction (PCR) analysis was performed to identify pathogenic YP and YE. Twenty-five percent (10 of 40) of the cases were positive for pathogenic Yersinia by P CR (four YE, four YP, and two with both species). Prominent histologic feat ures included epithelioid granulomas with lymphoid cuffing, transmural infl ammation with lymphoid aggregates, mucosal ulceration, and cryptitis. One Y ersinia-positive case contained mural Gram-negative bacilli; fungal and aci d-fast bacilli stains were all negative. Except fur one culture-negative ca se, serologies and cultures were not done or results were unavailable. Two Yersinia-positive patients were diagnosed subsequently with Crohn's disease , suggesting a possible relationship between the two entities. No other pat ients developed significant sequelae. YE and YP are important causes of gra nulomatous appendicitis, and Yersinia infection may mimic Crohn's disease. No histologic features distinguish reliably between Yersinia species, or be tween Yersinia-positive and Yersinia-negative cases. Because special stains and cultures are often not diagnostic, PCR analysis is an excellent techni que for the diagnosis of Yersinia.