Microscopic colitis: a modern view on the problem

Microscopic colitis (MC) is a chronic inflammatory disease of the colon characterized by watery diarrhea without blood admixture and normal or minimally altered endoscopic findings. The study’s relevance stems from the increasing prevalence of MC (11.4 cases per 100,000 person‑years in Western countries), its frequent underdiagnosis in primary care, and its significant impact on patients’ quality of life. MC is identified in 10% of individuals with chronic non‑bloody diarrhea, highlighting the need for deeper exploration of its etiology, pathogenesis, and diagnostic approaches. Objective — to systematize current scientific data on the etiology, pathogenesis, clinical manifestations, diagnosis, and treatment of MC, as well as to investigate its association with autoimmune diseases. Materials and methods. A systematic review of scientific literature was conducted, including prospective, multicenter, and population‑based studies evaluating risk factors, pathogenetic mechanisms, and therapeutic approaches to MC. Results. MC is more commonly diagnosed in women and individuals over 50 years, associated with autoimmune diseases (OR 5.5), genetic factors (HLA haplotype 8.1), gut microbiota dysbiosis (depletion of Clostridiales, predominance of Prevotella), infections (Clostridium difficile, Campylobacter concisus), and factors such as smoking (OR 3.58) and the use of proton pump inhibitors, non‑steroidal anti‑inflammatory drugs, or selective serotonin reuptake inhibitors. Histological examination of colon biopsies remains the gold standard for diagnosis, while budesonide is the primary treatment for inducing remission (81% efficacy). Conclusions. MC is a significant cause of chronic diarrhea, requiring differential diagnosis, particularly in patients with autoimmune conditions and nonspecific symptoms. Dysbiosis, genetic predisposition, and external triggers play key roles in its pathogenesis. Further research is needed to identify biomarkers, elucidate mechanisms of MC subtype transformation, and develop personalized therapeutic strategies.