Crohn's disease and ulcerative colitis in the same patient

Pathology and pathogenesis of diverticular disease and patterns of colonic mucosal changes overlying the diverticula

The aim of this article is to review the pathology of diverticular disease and draw attention to the histological changes that affect the wall and the mucosal lining of the sigmoid colon in this common condition. We were the first group to propose a histological classification for sigmoid colitis-associated diverticular disease, and in this paper we are adding another feature to our original observation.

Colitis and intestinal inflammation in IL10-/- mice results from IL-13Rα2-mediated attenuation of IL-13 activity

BACKGROUND & AIMS

The cytokine interleukin (IL)-10 is required to maintain immune homeostasis in the gastrointestinal tract. IL-10 null mice spontaneously develop colitis or are more susceptible to induction of colitis by infections, drugs, and autoimmune reactions. IL-13 regulates inflammatory conditions; its activity might be compromised by the IL-13 decoy receptor (IL-13Rα2).

METHODS

We examined the roles of IL-13 and IL-13Rα2 in intestinal inflammation in mice. To study the function of IL-13Rα2, il10(-/-) mice were crossed with il13rα2(-/-) to generate il10(-/-)il13rα2(-/-) double knockout (dKO) mice. Colitis was induced with the gastrointestinal toxin piroxicam or Trichuris muris infection.

RESULTS

Induction of colitis by interferon (IFN)-γ or IL-17 in IL-10 null mice requires IL-13Rα2. Following exposure of il10(-/-) mice to piroxicam or infection with T muris, production of IL-13Rα2 increased, resulting in decreased IL-13 bioactivity and increased inflammation in response to IFN-γ or IL-17A. In contrast to il10(-/-) mice, dKO mice were resistant to piroxicam-induced colitis; they also developed less severe colitis during chronic infection with T muris infection. In both models, resistance to IFN-γ and IL-17-mediated intestinal inflammation was associated with increased IL-13 activity. Susceptibility to colitis was restored when the dKO mice were injected with monoclonal antibodies against IL-13, confirming its protective role.

CONCLUSIONS

Colitis and intestinal inflammation in IL10(-/-) mice results from IL-13Rα2-mediated attenuation of IL-13 activity. In the absence of IL-13Rα2, IL-13 suppresses proinflammatory Th1 and Th17 responses. Reagents that block the IL-13 decoy receptor IL-13Rα2 might be developed for inflammatory bowel disease associated with increased levels of IFN-γ and IL-17.

Ulcerative colitis and Crohn's disease: is Mycobacterium avium subspecies paratuberculosis the common villain?

Mycobacterium avium, subspecies paratuberculosis (MAP) causes a chronic disease of the intestines in dairy cows and a wide range of other animals, including nonhuman primates, called Johne's ("Yo-knee's") disease. MAP has been consistently identified by a variety of techniques in humans with Crohn's disease. The research investigating the presence of MAP in patients with Crohn's disease has often identified MAP in the "negative" ulcerative colitis controls as well, suggesting that ulcerative colitis is also caused by MAP. Like other infectious diseases, dose, route of infection, age, sex and genes influence whether an individual infected with MAP develops ulcerative colitis or Crohn's disease. The apparently opposite role of smoking, increasing the risk of Crohn's disease while decreasing the risk of ulcerative colitis, is explained by a more careful review of the literature that reveals smoking causes an increase in both diseases but switches the phenotype from ulcerative colitis to Crohn's disease. MAP as the sole etiologic agent of both ulcerative colitis and Crohn's disease explains their common epidemiology, geographic distribution and familial and sporadic clusters, providing a unified hypothesis for the prevention and cure of the no longer "idiopathic" inflammatory bowel diseases.

Indeterminate colitis

A diagnosis of Crohn's disease (CD) and ulcerative colitis (UC) is based on a combination of clinical, histologic, endoscopic, and radiologic data. The distinction between UC and CD can be difficult because of the lack of a differentiating single gold standard. Indeterminate colitis (IC) was introduced by pathologists for the diagnosis of surgical colectomy specimens showing an overlap between the features of UC and CD. The diagnosis of IC was based on macroscopic and microscopic features. The term indeterminate colitis is in recent years more widely applied to include all cases with endoscopic, radiographic, and histologic evidence of chronic inflammatory bowel disease confined to the colon, but without fulfilment of diagnostic criteria for UC and CD. As for UC and CD, the diagnosis of IC has therefore become a clinicopathologic diagnosis. IC is generally considered to be a temporary diagnosis. The clinical characteristics of patients with IC are, however, somewhat different from the characteristics of those with UC. Furthermore, serologic markers such as perinuclear antineutrophil cytoplasmic antibody and anti-Saccharomyces cerevisiae, which are strongly linked with UC and CD, are both negative in a subset of patients with IC. Therefore, the possibility that IC could be a separate entity must be investigated.

The differential diagnosis of Crohn's disease and ulcerative colitis

Most cases of inflammatory bowel disease (IBD) can be correctly labelled as Crohn's disease (CD) or ulcerative colitis (UC) with careful initial gross and microscopic examination of biopsy and resection specimens together with close clinical and radiological correlation. Until we understand more of the aetiology and immunology of IBD we should admit that there are limitations imposed by current diagnostic criteria, consider the use of reporting proforma to improve diagnostic accuracy, and accept that in a small number of patients clinicopathological features will overlap, and CD may masquerade as UC.

The differential diagnosis of idiopathic inflammatory disease by colorectal biopsy

The differential diagnosis of idiopathic inflammatory bowel disease by colorectal biopsy poses a challenge to the endoscopist as well as the pathologist. Distinguishing non-idiopathic colitis from idiopathic colitis is the fundamental first step. No single histopathologic feature distinguishes between non-idiopathic and idiopathic inflammatory bowel disease or between the two forms of idiopathic inflammatory bowel disease (ulcerative colitis and Crohn's disease involving the colon). Interaction between the endoscopist and pathologist is essential in optimizing the contribution of colorectal biopsy to management of patients with inflammatory bowel disease.

Coexistent ulcerative colitis and Crohn's disease

This case report describes a patient with chronic ulcerative colitis and epithelial dysplasia of 17 y duration ultimately complicated by colonic carcinoma. At laparotomy, clinically unsuspected but typical Crohn's disease of the terminal ileum was also found. The macroscopic and histological features of the resected terminal ileum were characteristic of Crohn's disease.

Forms of colitis--a review of recent developments

Recent advances in the accessibility of the bowel and in techniques for the study of colonic pathology have resulted in descriptions of several forms of colitis which were previously unrecognized and in elucidation of the etiology of previously described but poorly understood entities. Present knowledge of antibiotic-associated colitis, colitis indeterminate, acute self-limited colitis, collagenous colitis and the colitis of food allergy is reviewed.