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Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 14, 2016; 22(38): 8459-8471
Published online Oct 14, 2016. doi: 10.3748/wjg.v22.i38.8459
Towards a new paradigm of microscopic colitis: Incomplete and variant forms
Danila Guagnozzi, Stefania Landolfi, Maria Vicario
Danila Guagnozzi, Department of Gastroenterology, Hospital Universitario Vall d’Hebron, 08035 Barcelona, Spain
Stefania Landolfi, Department of Pathology, Hospital Universitario Vall d’Hebron, 08035 Barcelona, Spain
Maria Vicario, Translational Mucosal Immunology Lab, Digestive Diseases Research Unit, Vall d’Hebron Institut de Recerca, Department of Gastroenterology. Hospital Universitario Vall d’Hebron, Universitat Autónoma de Barcelona, 08035 Barcelona, Spain
Maria Vicario, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 08035 Barcelona, Spain
Author contributions: All authors equally contributed to this paper with conception and design of the study, literature review and analysis, drafting and critical revision and editing, and final approval of the final version.
Supported by Fondo de Investigación Sanitaria, Instituto de Salud Carlos III, Subdirección General de Investigación Sanitaria, Ministerio de Economía y Competitividad, CP10/00502, PI13/00935 and CIBERehd, CB06/04/0021 (MV).
Conflict-of-interest statement: No potential conflicts of interest. No specific financial support.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Danila Guagnozzi, MD, Department of Gastroenterology, Hospital Universitario Vall d’Hebron, Passeig Vall d’Hebron 119-129, 08035 Barcelona, Spain. danila_g@libero.it
Telephone: +34-934894035 Fax: + 34-934894032
Received: May 29, 2016
Peer-review started: May 30, 2016
First decision: July 13, 2016
Revised: August 20, 2016
Accepted: September 8, 2016
Article in press: September 8, 2016
Published online: October 14, 2016
Processing time: 136 Days and 8.5 Hours
Abstract

Microscopic colitis (MC) is a chronic inflammatory bowel disease that has emerged in the last three decades as a leading cause of chronic watery diarrhoea. MC classically includes two main subtypes: lymphocytic colitis (LC) and collagenous colitis (CC). Other types of histopathological changes in the colonic mucosa have been described in patients with chronic diarrhoea, without fulfilling the conventional histopathological criteria for MC diagnosis. Whereas those unclassified alterations remained orphan for a long time, the use of the term incomplete MC (MCi) is nowadays universally accepted. However, it is still unresolved whether CC, LC and MCi should be considered as one clinical entity or if they represent three related conditions. In contrast to classical MC, the real epidemiological impact of MCi remains unknown, because only few epidemiological studies and case reports have been described. MCi presents clinical characteristics indistinguishable from complete MC with a good response to budesonide and cholestiramine. Although a number of medical treatments have been assayed in MC patients, currently, there is no causal treatment approach for MC and MCi, and only empirical strategies have been performed. Further studies are needed in order to identify their etiopathogenic mechanisms, and to better classify and treat MC.

Keywords: Microscopic colitis; Incomplete microscopic colitis; Collagenous colitis; Lymphocytic colitis

Core tip: Microscopic colitis (MC) includes two well-defined entities: collagenous colitis and lymphocytic colitis. Similar clinical manifestations, but variable histopathologic features have also been identified and recognized as additional forms of MC, as not all patients suffering from colitis fulfill the criteria for MC diagnosis. Introducing the histological diagnosis for incomplete MC subtypes could reduce the risk of missing patients with a treatable cause of chronic diarrhoea. The importance of developing research studies addressed at describing etiopathogenic mechanisms of MC subtypes is highlighted in this review.