Towards a new paradigm of microscopic colitis: Incomplete and variant forms

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.

Mechanical complications of acute myocardial infarction considering risk factors, treatment and survival of patients in 10-year clinical observation

“…Nonetheless, other research showed that no change in the mean thickness of the collagen band had been reported, even after trea tment with Budesonide [1,5,6]. On the other hand, it seems likely that the change of one subtype of MC to another one is quite possible [4]. Researchers from the Karolinska Institutet Marie-Rose Mellander [10] reported such observations during an MC cohort: "Histological change of phenotype over time was not uncommon and was observed in 12% of the patients (10 CC to LC, 13 LC to CC)".…”

“…The apparent incidence and prevalence of MC is much higher than initially thought. Increases in the reported incidence are observed [4]. Is this a genuine rise in incidence rates or rather the consequence of better detection of the disease?…”

“…There are some studies reporting good clinical response to methotrexate, thiopurines and anti-TNF therapy in patients with active MC. Unfortunately, the data is insufficient to consider them to be definite therapies [4,5]. The histological findings of MC were inconsistent with repeat endoscopy.…”

“…Is the disappearance of collagen bands possible? Some researchers assume that histologic resolution of CC is probable and it is associated with the disappearance of symptoms [4]. Nonetheless, other research showed that no change in the mean thickness of the collagen band had been reported, even after trea tment with Budesonide [1,5,6].…”

Collagenous panenteritis: a rare cause of chronic diarrhoea

“…The diagnosis of collagenous colitis is characterised by irregular thickened collagen band (>10 μm) beneath the surface epitelium 15. The advent of high-definition colonoscopes has led to discovery of distinctive endoscopic findings such as pseudomembranes, pruning of the mucosal vascular pattern and mucosal breaks in association with collagenous colitis 16 17…”