Inflammatory eye disease is a risk factor for future microscopic colitis: A nationwide population-based matched case control study.

BACKGROUND: Microscopic colitis (MC) is an inflammatory disorder of the colon. To date, the relationship between inflammatory eye diseases and MC is unclear. OBJECTIVE: To assess whether inflammatory eye disease (iridocyclitis and episcleritis) is a risk factor for MC. METHODS: We conducted a nationwide matched case control study in Sweden leveraging the ESPRESSO-study (a Swedish database containing data on all biopsies from the gastrointestinal tract from 1965 to 2017). In total, we identified 14,338 patients with biopsy-verified MC (diagnosed from 1981 to 2017). Patients with MC were matched (by age, sex, county and year of birth) with 68,753 controls from the general population and the occurrence of preceding inflammatory eye diseases (defined as diagnosis of episcleritis or iridocyclitis) in the two groups was compared. Multivariable adjusted odds ratios (aORs) were calculated using conditional logistic regression conditioned on the matching variables. RESULTS: A majority of patients with MC were women (71.9%) and the median age at MC diagnosis was 63.3 years (interquartile range (IQR) = 50.7-72.6). Some 225 (1.6%) MC patients had an earlier record of inflammatory eye disease compared with 614 (0.9%) in controls. These figures corresponded to an aOR of 1.77 (95% CI = 1.52-2.07) for inflammatory eye diseases in patients with MC. Compared to siblings, the aOR for previous inflammatory eye diseases in MC was 1.52 (95% CI = 1.17-1.98) and patients treated with budesonide, as a proxy for clinically significant disease, had a somewhat higher aOR for previous inflammatory eye diseases. CONCLUSION: Inflammatory eye diseases are more common in patients subsequently being diagnosed with MC. Our findings highlight that these conditions may have shared causes and inflammatory pathways and are of clinical interest to gastroenterologists, ophthalmologists and general practitioners.

Factors associated with long-term clinical outcome in microscopic colitis.

BACKGROUND AND AIMS: Microscopic colitis has been increasingly recognized as a cause of chronic diarrhoea. We aimed to characterize the role of disease-related factors and treatments on the clinical outcomes of microscopic colitis. METHODS: We retrospectively reviewed the medical records of patients with microscopic colitis who were treated at the University of Chicago and Oregon Health & Science University between August 2010 and May 2016. Patient characteristics and treatments were evaluated as predictors of clinical outcomes using univariate and multivariate analyses. Clinical remission was defined as no symptoms associated with microscopic colitis based on physician assessment and histologic remission was defined as no evidence of histological inflammation of microscopic colitis. RESULTS: Seventy-two patients with microscopic colitis were included in the study (28 with lymphocytic colitis and 44 with collagenous colitis). Non-steroidal anti-inflammatory drugs, proton pump inhibitors and selective serotonin reuptake inhibitors were used in 23 (31.9%), 14 (19.4%) and 15 (20.8%), respectively, at the time of diagnosis. Among 46 patients with adequate follow-up data, 25 (54.3%) patients achieved clinical remission. Response to budesonide (p = .0002) and achieving histologic remission (p = .0008) were associated with clinical remission on univariate analysis. On multivariate analysis, budesonide response (p = .0052) was associated with clinical remission (odds ratio 25.00, 95% confidence interval 2.63-238.10). Among 22 patients who underwent a follow-up colonoscopy, five patients (22.7%) achieved histologic remission. All patients with histologic remission maintained clinical remission without medication, whereas only two patients (11.8%) were able to discontinue medical therapy when histologic inflammation was present (p = .0002). CONCLUSIONS: In the present cohort of patients with microscopic colitis, a favourable response to budesonide was significantly associated with long-term clinical remission, and all patients achieving histological remission were able to maintain clinical remission without further medical therapy. Larger studies are required to confirm these findings.

Microscopic colitis related to food supplement containing turmeric: a review of 3 cases.

Microscopic colitis is a chronic inflammatory disorder of the colon characterized by microscopic changes in the intestinal lining. Turmeric, a commonly used spice, is generally regarded as beneficial for digestive and articular health thanks to its anti-inflammatory properties. No cases of microscopic colitis under a food supplement containing turmeric has been previously described in the literature. This article highlights 3 cases where the consumption of a specific turmeric-based supplement caused microscopic colitis. Each of them complained about profuse watery diarrhea shortly after initiating the food supplement containing turmeric. Ileo-colonoscopies with biopsies confirmed the diagnosis of microscopic colitis, with two cases classified as lymphocytic colitis and the third as collagenous colitis. Following the discontinuation of the supplement, all patients experienced a resolution of their symptoms within a few days. Subsequent control biopsies for the three patients confirmed the resolution of microscopic colitis.

WARNING TO DELAY IN DIAGNOSING MICROSCOPIC COLITIS IN OLDER ADULTS. A SERIES OF CASES.

BACKGROUND: Microscopic colitis (MC) is a chronic inflammatory bowel disease causing non-bloody diarrhea, and several cases are undiagnosed as a hidden cause of chronic diarrhea. OBJECTIVE: We aimed to report the symptoms, delay diagnosis and the treatment of MC in a case series. METHODS: All patients were treated at a Gastroenterology reference office from May 2022 to June 2023. Personal history including preexisting disorders, use of medications and smoking habits were collected. The delay between the onset of symptoms and the correct diagnosis was informed. All patients consented to use budesonide MMX (Corament®) off label. RESULTS: During the study period, six Caucasoid patients were diagnosed with MC, five females and one male, between the ages of 65 and 74. All patients had comorbities and were taking multiple prescription drugs. Laboratory findings showed negative serology for celiac disease for all patients, normal levels of albumin and vitamin B12. The delay between the symptoms and the MC diagnosis varied from 2 months to 6 years. All patients had a previous diagnosis of irritable bowel syndrome. All patients were in complete clinical remission during the treatment and referred no side effects of the drug. CONCLUSION: Older females using high-risk medications are suggestive of MC. Preventing delay in the diagnosis of MC is crucial to improvement in patients´ quality of life. Budesonide MMX appears to be effective, safe and well-tolerated. BACKGROUND: • Microscopic Colitis is a chronic inflammatory bowel disease causing non-bloody diarrhea. BACKGROUND: • Several cases are undiagnosed and can be a hidden cause of chronic diarrhea. BACKGROUND: • Treatment with budesonide MMX (Corament®, off label) was effective and safe.

Diagnosis and Pharmacological Management of Microscopic Colitis in Geriatric Care.

Microscopic colitis, a diagnosis under the umbrella term of inflammatory bowel disease, is a prevalent cause of watery diarrhea, often with symptoms of urgency and bloating, typically observed in older adults aged ≥ 60 years. Its incidence has been reported to exceed those of ulcerative colitis and Crohn's disease in some geographical areas. Although nonpathognomonic endoscopic abnormalities, including changes of the vascular mucosal pattern; mucosal erythema; edema; nodularity; or mucosal defects, e.g., "cat scratches" have been reported, a colonoscopy is typically macroscopically normal. As reliable biomarkers are unavailable, colonoscopy using random biopsies from various parts of the colon is compulsory. Based on the histological examination under a microscope, the disease is divided into collagenous (with a thickened subepithelial collagenous band) and lymphocytic (with intraepithelial lymphocytosis) colitis, although incomplete forms exist. In routine clinical settings, the disease has a high risk of being misdiagnosed as irritable bowel syndrome or even overlooked. Therefore, healthcare providers should be familiar with clinical features and rational management strategies. A 6-8-week oral budesonide treatment course (9 mg/day) is considered the first-line therapy, but patients often experience relapse when discontinued, or might become intolerant, dependent, or even fail to respond. Consequently, other therapeutic options (e.g., bismuth subsalicylate, biologics, loperamide, bile acid sequestrants, and thiopurines) recommended by available guidelines may be prescribed. Herein, clinically meaningful data is provided based on the latest evidence that may aid in reaching a diagnosis and establishing rational therapy in geriatric care to control symptoms and enhance the quality of life for those affected.

Clinical Implications of Microscopic Colitis Isolated to Polyps.

Microscopic colitis is generally identified on random colon biopsies performed for chronic diarrhea, but rarely incidental polyps have histologic features of microscopic colitis. We compared patients with polypoid microscopic colitis to control patients with conventional polyps to determine the implications of polypoid microscopic colitis.Medical records were searched for patients without prior or concurrent microscopic colitis who were found to have polypoid microscopic colitis. For each patient with polypoid microscopic colitis, one patient with conventional polyps was selected as a control. We reviewed the histologic features of each polypoid microscopic colitis specimen, and evaluated endoscopic and clinical findings for polypoid microscopic colitis patients and controls.Twenty-six patients with polypoid microscopic colitis were identified with histologic features of collagenous colitis in 8 patients (31%) and lymphocytic colitis in 18 patients (69%). Polypoid microscopic colitis was unifocal in 14 patients (54%) and multifocal in 12 patients (46%). Patients with polypoid microscopic colitis were older than control patients (median age = 60 years vs 66 years, P = .04). On follow-up 7 patients with polypoid microscopic colitis (33%) developed chronic diarrhea compared to 3 (12%) controls (P = .16). Of patients with follow-up biopsies, 1 patient with polypoid microscopic colitis (13%) and no control patients developed microscopic colitis (P = 1).Polypoid microscopic colitis may be identified in asymptomatic patients and most patients do not develop chronic diarrhea, but some patients with polypoid microscopic colitis develop diarrhea (33% vs 12% in controls) or conventional microscopic colitis on follow-up. Thus pathologists should distinguish polypoid microscopic colitis from conventional microscopic colitis but may inform clinicians of the uncertain association with chronic diarrhea to guide decisions regarding follow-up.

Microscopic Colitis: A Diagnostic Challenge in Patients with Irritable Bowel Syndrome.

BACKGROUND AND AIMS: Irritable Bowel Syndrome (IBS) is one of the most frequently diagnosed gastrointestinal disease with a prevalence of 4.1% in the general population. It is diagnosed using the Rome IV criteria. Microscopic colitis (MC), collagenous/lymphocytic colitis is a cause of chronic, watery, non-bloody diarrhea. It is a real challenge to diagnose MC in patients with IBS. The aims of the study were to determine the prevalence of MC in patients initially diagnosed with IBS, as well as to correlate fecal calprotectin levels with the endoscopic findings and microscopic inflammation in MC. METHODS: This is a retrospective study conducted in a single tertiary center with over 89 IBS patients for a period of 4 years. The patients included were patients diagnosed with IBS predominant diarrhea (IBS-D) and mixed IBS (IBS-M) using the Rome IV criteria. Total colonoscopy was performed in these patients, multiple biopsies being taken and calprotectin levels were measured. RESULTS: Out of a total of 89 IBS-D patients, 58 patients (65.2%) had no microscopic lesions, 12 patients (13.5%) had diverticular disease, 9 patients (10.1%) had non-specific chronic inflammation of the colon mucosa and 10 patients (11.2%) were diagnosed with MC. The calprotectin levels ranged from 49 µg/g to 213 µg/g. Of a total of 10 patients diagnosed with MC, 6 (60%) of them had calprotectin levels <100 µg/g and 4 (40%) had calprotectin levels >100 µg/g. The fecal calprotectin levels were higher in patients diagnosed with MC compared to those who had no microscopic lesions at the histological exam and it was also correlated with the grade of colonic microscopic inflammation. CONCLUSIONS: Microscopic colitis is less familiar to physicians and can be clinically misdiagnosed as IBS-D. An early and correct diagnosis is important for an accurate therapy.

What do we know today about drug-induced microscopic colitis? A case of lymphocytic colitis on olmesartan.

Microscopic colitis is part of the differential diagnosis of chronic watery diarrhea. Colonoscopy discloses a normal looking mucosa, therefore its diagnosis is based on histology of colonic biopsies. Two main phenotypes are distinguished: collagenous colitis and lymphocytic colitis. A third entity, incomplete microscopic colitis or unspecified microscopic colitis has been reported in the literature. It affects preferentially women over 60 years of age and its association with certain drugs is increasingly established. In case of suspected drug-induced microscopic colitis, identification of the responsible drug is a key to management. After discontinuation of the suspected drug, the gold standard of treatment is budesonide both for induction and for maintenance in case of clinical relapse, as is often the case after discontinuation. Therapy with immunomodulators, biologics, or surgery is reserved for refractory forms of microscopic colitis after multidisciplinary consultation. Through the clinical case of colitis on olmesartan, we will review the latest recommendations on drug-induced microscopic colitis.

Microscopic colitis and risk of incident rheumatoid arthritis: A nationwide population-based matched cohort study.

BACKGROUND: Microscopic colitis (MC) has been linked to several autoimmune conditions. Results from previous studies on the association with rheumatoid arthritis (RA) have been inconsistent. AIM: To assess the risk of future RA in MC. METHODS: We conducted a nationwide matched cohort study in Sweden of 8179 patients with biopsy-verified MC (diagnosed in 2007-2017), 36,400 matched reference individuals and 8202 siblings without MC, with follow-up until 2021. Information on MC was obtained from all of Sweden's regional pathology registers (n = 28) through the ESPRESSO cohort. Data on incident RA were collected from the National Patient Register. Using Cox regression, we calculated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs). RESULTS: During a median follow-up of 9.1 years (interquartile range = 6.7-11.7), 73 MC patients and 183 reference individuals from the general population were diagnosed with RA (99 vs. 55 events per 100,000 person-years), equivalent to one extra case of RA in 226 patients with MC followed for 10 years. These rates corresponded to an aHR of 1.83 (95% CI = 1.39-2.41). The aHR was highest during the first year of follow-up (2.31 [95% CI = 1.08-4.97]) and remained significantly elevated up to 5 years after MC diagnosis (aHR 2.16; 95% CI = 1.42-3.30). Compared to siblings, without MC, the aHR was 2.04 (95% CI = 1.18-3.56). CONCLUSION: Patients with MC are at a nearly two-fold risk of developing RA compared to the general population. Knowledge of this increased risk may expedite evaluation for RA in patients with MC presenting with joint symptoms and/or arthralgia, thus preventing delay until RA diagnosis.

Regional differences in the incidence of lymphocytic and collagenous colitis over time.

BACKGROUND: In microscopic colitis (MC), the incidence has increased over the last decades. The aim of the present study was to determine the incidence of lymphocytic (LC) and collagenous colitis (CC) in the county Skåne (Scania), southern Sweden, during the period 2010-20 with focus both on the temporal and spatial variations. METHODS: The MC diagnosis was retrieved from the biopsy registries at the Departments of Pathology. Established diagnostic criteria (increased lymphocyte count, inflammation in lamina propria and in CC a collagen band) were used for diagnosis. Age, gender, date for diagnosis and municipality of residence were retrieved for all patients. RESULTS: In total 1985 patients could be identified with a mean age of 62.9 years (SD 15.7) whereof 1415 were women. The incidence for CC was stable with a total age-standardized rate (ASR) per 100 000 person-years of 6.34, (range 4.6-8.1). In LC the ASR was 7.90 (range 1.7-15.2) but increased markedly 2015-20 reaching 15.2 in 2019. Also, the northwest part of the region showed significantly higher ASR:s of LC during the last part of the decade in comparation to the whole region. CONCLUSIONS: The incidence of CC was stable during the period while LC differed substantially in a way that indicates that it most probably must be two different disease entities. In LC, in view of the marked and rapid increase, although no definitive explanation could be found, causative environmental factors could be contemplated, why further studies are indicated.

MICROSCOPIC COLITIS: CONSIDERATIONS FOR GASTROENTEROLOGISTS, ENDOSCOPISTS, AND PATHOLOGISTS.

•Diagnosis of microscopic colitis necessitates effective communication among gastroenterologists, endoscopists, and pathologists. •The gastroenterologist should refer every patient with chronic watery diarrhea to perform a colonoscopy in spite of the benign course of the disease and the absence of alarm symptoms. •The endoscopist should take 2 or 3 biopsy samples of the colonic mucosa from the right and left colon, put in separate recipients, despite that the mucosa looked macroscopically normal. •The pathologist should be encouraged to use objective histological criteria to make the diagnosis. Microscopic colitis is a chronic inflammatory bowel disease characterized by non-bloody diarrhea that can range from mild to severe. It is difficult to attribute up to 10-20% of chronic diarrhea to microscopic colitis. The three determinants factors of the diagnosis are characteristic clinical symptoms, normal endoscopic picture of the colon, and pathognomonic histological picture. This manuscript aimed to update considerations and recommendations for professionals involved (gastroenterologist, endoscopists and pathologist) in the diagnosis of MC. In addition, a short recommendation about treatment.

Dietary Calcium and Risk of Microscopic Colitis.

BACKGROUND: Microscopic colitis (MC) is an increasingly common cause of watery diarrhea particularly in older individuals. The role of diet in MC has received little study. METHODS: We conducted a case-control study at a single institution enrolling patients referred for elective outpatient colonoscopy for diarrhea. Patients were classified as cases with MC or non-MC controls after a review of colon biopsies by 1 research pathologist. Study subjects were interviewed by a trained telephone interviewer using a validated food frequency questionnaire. Adherent microbes were evaluated from colonic biopsies using 16s rRNA sequencing. RESULTS: The study population included 106 cases with MC and 215 controls. Compared with controls, the cases were older, better educated, and more likely to be female. Cases with MC had lower body mass index and were more likely to have lost weight. Subjects in the highest quartile of dietary calcium intake had a lower risk of MC compared with those in the lowest quartile (adjusted odds ratio 0.22, 95% confidence interval 0.07-0.76). The findings were not explained by dairy intake, body mass index, or weight loss. We found that dietary calcium intake had significant associations with the abundance of Actinobacteria and Coriobacteriales in the microbial community of colonic biopsies. DISCUSSION: Compared with patients with diarrhea, cases with MC had a lower intake of dietary calcium. Diet can be associated with alterations in the gut microbiota and with luminal factors that could affect the risk of MC.

Type 1 diabetes and microscopic colitis: A nationwide matched case-control study in Sweden.

BACKGROUND AND AIMS: Microscopic colitis (MC) is a colonic inflammatory condition associated with autoimmune dysfunction. Type 1 diabetes (T1D) is a chronic disease induced by autoimmune destruction of pancreatic ß-cells. We aimed to examine the association between T1D and MC. METHODS: A matched case-control study was conducted using the nationwide ESPRESSO cohort as study base. All biopsy-confirmed MC patients born after 1940 were identified and compared to biopsy-free individuals matched from the general population for T1D diagnosis using the Swedish National Patient Register. The T1D-MC association was estimated as odds ratios (ORs) and 95% confidence intervals (CIs) by conditional logistic models, considering differences by sex and MC subtype. Full sibling comparison and adjustment for MC-associated medications were also performed. RESULTS: We identified 352 (3.7%) and 945 (2.0%) T1D diagnoses from 9,600 MC cases and 47,870 matched population controls, respectively, which corresponded to an overall OR of 1.79 (95% CI: 1.56-2.05). The association was stronger for collagenous colitis (OR, 2.15; 95% CI: 1.70-2.71) than lymphocytic colitis (OR, 1.62; 95% CI: 1.37-1.92) and remained statistically significant in full sibling comparison (OR, 1.46; 95%: 1.18-1.81). Medication adjustment attenuated the association to null among females (OR: 1.02; 95% CI: 0.82-1.27) but not among males (OR: 1.45; 95% CI: 1.11-1.90). CONCLUSION: T1D diagnosis was almost 80% more prevalent in MC patients compared to general population. This positive association did not seem to be spurious due to residual confounding shared by full siblings but may relate to consumption of medications associated with MC onset.

Celiac disease and risk of microscopic colitis: A nationwide population-based matched cohort study.

BACKGROUND: An association has been reported between celiac disease (CD) and microscopic colitis (MC). However, large, population-based cohort studies are rare. OBJECTIVE: To systematically examine the association between CD and MC in a large, nationwide cohort. METHODS: We conducted a nationwide population-based matched cohort study in Sweden of 45,138 patients with biopsy-verified CD (diagnosed in 1990-2016), 223,149 reference individuals, and 51,449 siblings of CD patients. Data on CD and MC were obtained from all (n = 28) pathology departments in Sweden. Adjusted hazard ratios (aHRs) were calculated using Cox regression. RESULTS: During follow-up, 452 CD patients and 197 reference individuals received an MC diagnosis (86.1 vs. 7.5 per 100,000 person-years). This difference corresponded to an aHR of 11.6 (95% confidence interval [CI] = 9.8-13.8) or eight extra MC cases in 1000 CD patients followed up for 10 years. Although the risk of MC was highest during the first year of follow-up (aHR 35.2; 95% CI = 20.1-61.6), it remained elevated even after 10 years (aHR 8.1; 95% CI = 6.0-10.9). Examining MC subtypes lymphocytic colitis (LC) and collagenous colitis (CC) separately, the aHR was 12.4 (95% CI = 10.0-15.3) for LC and 10.2 (95% CI = 7.7-13.6) for CC. MC was also more common before CD (adjusted odds ratio [aOR] = 52.7; 95% CI = 31.4-88.4). Compared to siblings, risk estimates decreased but remained elevated (CD and later MC: HR = 6.2; CD and earlier MC: aOR = 7.9). CONCLUSION: Our study demonstrated a very strong association of MC with CD with an increased risk of future and previous MC in CD patients. The magnitude of the associations underscores the need to consider the concomitance of these diagnoses in cases in which gastrointestinal symptoms persist or recur despite a gluten-free diet or conventional MC treatment. The comparatively lower risk estimates in sibling comparisons suggest that shared genetic and early environmental factors may contribute to the association between CD and MC.

Microscopic colitis: lymphocytic colitis, collagenous colitis, and beyond.

Microscopic colitis (MC) is a chronic inflammatory disease of colon with clinical presentations of chronic, watery, nonbloody diarrhea, and normal or almost normal endoscopic findings. Confirmation of a diagnosis of MC requires microscopic examination on colon biopsy to identify characteristic morphological features, in which 2 main subtypes of MC, lymphocytic colitis (LC) and collagenous colitis (CC), have been described. Although the pathogenesis of MC is still unclear, studies have revealed associations of MC with many risk factors and other diseases such as celiac disease, inflammatory bowel disease, and medication use. Meanwhile, variants of MC, MC incomplete, or MC-like changes in other conditions are still diagnostic dilemmas for pathologists. The goal of this paper is to systemically introduce the clinicopathologic features of MC and focus on unusual features of MC and its associations with other conditions.

Frequency And Risk Factors Of Microscopic Colitis As A Cause Of Chronic Watery Diarrhoea.

BACKGROUND: Microscopic colitis (MC) is one of the most underdiagnosed conditions leading to chronic watery diarrhoea in patients worldwide. This is the first study of this kind in Pakistan and we aimed to calculate the frequency as well as study the risk factors behind the disease. METHODS: This was a prospective cross-sectional study in a tertiary care hospital in Pakistan. A total of 58 participants with chronic watery diarrhoea who had normal colonoscopy were recruited for the study and biopsies were obtained for diagnosing MC. RESULTS: 2 participants out of 58 (3.4%) had biopsy proven microscopic colitis; one patient had a lymphocytic colitis variant and the other had a collagenous colitis variant. The average score based on the MC scoring system was 7.53 in the entire study group. The patient with lymphocytic colitis had a score of 06 while the patient with collagenous colitis had a score of 8. CONCLUSIONS: The frequency of microscopic colitis was found to be 3.4% of all cases of chronic watery diarrhoea. A link between MC and autoimmune diseases was also observed. However, we had a limited sample size and encouraged future studies to employ a larger sample size to get a multifaceted look at the disease process.

Microscopic colitis, a forgotten condition: a clinical case and review of the literature.

OBJECTIVE: Microscopic colitis is a not uncommon chronic inflammatory disease of the colon, characterized by watery, non-bloody diarrhea, which is often forgotten and misdiagnosed. CASE PRESENTATION: In this paper, we present a puzzling case of relapsing chronic diarrhea triggered by non-steroidal anti-inflammatory drug (NSAID) abuse, smoking, inappropriate antibiotic use, and secondary Clostridium Difficilis infection. Several tests were performed during hospitalization, all of which were negative apart from fecal calprotectin (> 6,000 mg/kg, normal values < 50 mg/kg) and a positive Clostridium Difficilis toxin test. Since Vancomycin treatment did not bring about the expected response, colonoscopy was performed, which led to diagnosis, targeted therapy, and clinical resolution. Targeted therapy with budesonide and probiotics was initiated leading to resolution of the diarrhea. CONCLUSIONS: This case study shows how actual diagnosis may be delayed not only due to having to perform differential diagnosis with chronic inflammatory diseases, but also because certainty can only come from histological evidence, which takes time to obtain, especially when the disease's multifactorial nature is considered (smoking, NSAID abuse, oral proton pump inhibitors, inappropriate antibiotic use, and Clostridium difficilis infection).

Microscopic colitis: Etiopathology, diagnosis, and rational management.

Microscopic colitis is an inflammatory bowel disease divided into two subtypes: collagenous colitis and lymphocytic colitis. With an increasing incidence of microscopic colitis exceeding those of ulcerative and Crohn's disease among elderly people in some countries, microscopic colitis is a debilitating life experience. Therefore, physicians should be familiar with its clinical features and management strategies because the disease deserves the same attention as the classical inflammatory bowel diseases. Here, state-of-the-art knowledge of microscopic colitis is provided from a global perspective with reference to etiopathology and how to establish the diagnosis with the overall aim to create awareness and improve rational management in clinical practice. The immune system and a dysregulated immune response seem to play a key role combined with risk factors (e.g. cigarette smoking) in genetically predisposed individuals. The symptoms are characterized by recurrent or chronic nonbloody, watery diarrhea, urgency, weight loss, and a female preponderance. As biomarkers are absent, the diagnosis relies on colonoscopy with a histological assessment of biopsy specimens from all parts of the colon. Although the disease is not associated with a risk of colorectal cancer, a recent nationwide, population-based cohort study found an increased risk of lymphoma and lung cancer. Budesonide is the first-line therapy for management, whereas immunomodulatory drugs (including biologics) and drugs with antidiarrheal properties may be indicated in those failing, dependent, or intolerant to budesonide. In microscopic colitis induced by checkpoint inhibitors, a drug class used increasingly for a wide range of malignancies, a more aggressive therapeutic approach with biologics introduced early seems reasonable. However, particular attention needs to be drawn to the existence of incomplete forms of microscopic colitis with the risk of being overlooked in routine clinical settings.