Microscopic colitis (MC) is a chronic relapsing disease of the colon, characterized by watery non-bloody diarrhea, usually normal colonoscopic findings, and typical histology findings. It is frequently accompanied by abdominal pain, nocturnal diarrhea, and mild weight loss. The incidence of MC has increased significantly over recent years with a 2010 study reporting U.S. incidence for MC as 19.7 per 100,000 person-years. MC comprises two major histological subtypes: collagenous colitis (CC), characterized by a distinctive thickened band of subepithelial collagen (\>10-20um), and lymphocytic colitis (LC), with an increased number of intraepithelial lymphocytes (\>20 lymphocytes per 100 epithelial cells).
Although the exact etiology of MC remains largely unknown, a few observational studies have suggested associations with autoimmune disorders (e.g. celiac disease, and thyroid disorders), cigarette smoking status, and medications such as non-steroidal anti-inflammatory drugs (NSAIDS), proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRI), and statins. In addition to environmental factors, recently studies indicate that genetics and specific infectious organisms may also play a role in development of the disease. A recent study revealed a seasonal incidence pattern of lymphocytic colitis, suggesting a potential link to an infectious or allergic component. Further, one study demonstrated an association between collagenous colitis and persistent colonic C. difficile infection. Additionally, while familial occurrence of MC has been reported, suggesting a genetic predisposition, the roles of specific genetic factors have not been described. Finally, recent studies demonstrate an association between MC and various autoimmune disorders including celiac disease, autoimmune thyroid disease, and Sjören's syndrome, indicating that MC may be part of a broader spectrum of autoimmune disorders. Despite these findings, few studies have investigated the role of genetic, infectious, and immunological factors in the development and progression of MC.
Budesonide is the only treatment for MC that appeared to be effective in randomized controlled trials, with remission rates of 80%. However, recurrence of clinical symptoms following withdrawal of treatment is not uncommon. Thus, further investigation of the molecular mechanisms underlying MC is needed in order to obtain targeted and sustainable treatment.
Analysis of clinical specimens obtained by colonoscopy from individuals affected with MC over the course of their treatment offers a promising method by which to improve our understanding of MC. Profiling of genetic and molecular characteristics such as changes in gut flora, colonic mucosal immune profiles, and genetic factors over the course of treatment would provide powerful insight into the role of these factors in the pathophysiology of the disease which may ultimately lead to better treatments. Additionally, identification of disease biomarkers can aid in developing disease monitoring and surveillance strategies.
Here, we propose to establish a cohort of individuals with suspected microscopic colitis undergoing diagnostic colonoscopy at the Massachusetts General Hospital (MGH) to identify genetic and molecular characteristics associated with the progression of this disease. This study will elaborate on findings from a medical record review of patients with microscopic colitis treated at MGH from 2002 to 2014. In addition to medical records, genetic and molecular characteristics of colonic samples will be examined to determine their influence on treatment response and outcomes.
