The fourth scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on the relevance of intestinal fibrosis in the disease course of inflammatory bowel disease (IBD). The objective was to better understand the pathophysiological mechanisms of intestinal fibrosis, to identify useful markers and imaging modalities of fibrosis in order to assess its presence and progression, and, finally, to point out possible approaches for the prevention and the treatment of fibrosis. The results of this workshop are presented in three separate manuscripts. This first section describes the most important mechanisms that contribute to the initiation and progression of intestinal fibrosis in IBD including the cellular and molecular mediators, the extracellular matrix molecules and matrix metalloproteinases/tissue inhibitors of metalloproteinases-system, the microbiota products, the role of fat, genetic and epigenetic factors, as well as the currently available experimental models. Furthermore, it identifies unanswered questions in the field of intestinal fibrosis and provides a framework for future research.

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

A subgroup of patients with inflammatory bowel disease (IBD) treated with anti-tumor necrosis factor (TNF) antibodies develop skin lesions, but the lesions and their clinical course are not well-characterized. To describe patients treated with anti-TNF antibodies who did and did not develop skin lesions. Retrospective cohort. Single IBD tertiary referral center. 917 consecutive patients with IBD who initiated anti-TNF therapy. Skin lesions, patient demographic characteristics, treatments, clinical course, and serologic and genetic markers. During a median follow-up of 3.5 years (interquartile range [IQR], 0.5 to 7.4 years), skin lesions associated with the use of anti-TNF therapy developed in 264 of 917 (29%) patients (psoriasiform eczema, 30.6%; eczema, 23.5%; xerosis cutis, 10.6%; palmoplantar pustulosis, 5.3%; psoriasis, 3.8%; other, 26.1%). Lesions typically developed at flexural regions, genitalia, and the scalp, especially the psoriasiform lesions. Thirty-one percent of women and 26% of men developed lesions. Median cumulative doses (2864 mg/y [IQR, 2203 to 3819 mg/y] and 2927 mg/y [IQR, 2377 to 3667 mg/y]) and trough levels (4.2 µg/mL [IQR, 2.6 to 5.8 µg/mL] and 4.0 µg/mL [IQR, 1.6 to 5.9 µg/mL]) of infliximab were similar in patients with and without lesions. All but 28 patients (11%) were successfully managed without needing to stop therapy because of lesions. Retrospective nature and no matched control group of patients not receiving anti-TNF therapy. Skin lesions occur frequently in association with anti-TNF therapy but rarely require discontinuation of therapy. Close surveillance and early referral to a dedicated dermatologist are recommended. Research Foundation Flanders (FWO), Belgium; Geconcerteerde Onderzoekacties of KU Leuven; and Janssen Biologics.