Description

• Microscopic colitis (MC) is a relatively common cause of chronic, recurrent nonbloody diarrhea with two subtypes: collagenous colitis (CC) and lymphocytic colitis (LC). MC is typically associated with autoimmune diseases and/or certain medications. Diagnosis requires colonic biopsy and histologic tissue analysis.
• No significant difference in management of collagenous versus LC

Epidemiology

Incidence

• Up to 20–30% of chronic diarrhea may be due to MC.
• Since 1985, the incidence in the United States has increased from 1 to 20 per 100,000 person-years.

Prevalence

• Prevalence ~103/100,000 persons
• More common in older individuals. The average age at diagnosis is 53 to 69 years.
• Female > male; ranging between 3:1 and 9:1

Etiology and Pathophysiology

• Unclear etiology; strong association with autoimmune diseases, smoking, and certain medications
• Models of pathogenesis include autoimmune destruction, inflammatory response to luminal factors, and myofibroblast dysfunction (for CC).
• Animal models suggest bacterial translocation may play a role by inducing an inflammatory cascade in colonic mucosa leading to increased mucosal permeability, cytokine release, degradation of collagen matrix, and dysregulation of subepithelial myofibroblasts.

Genetics
No specific genetic mutation has been identified but increased prevalence of human leukocyte antigen DR3 DQ2 allele noted in patients with MC.

Risk Factors

• Nonsteroidal anti-inflammatory drugs
• Proton pump inhibitors
• Statins
• β-Blockers
• Smoking

General Prevention

• Judicious use of associated medications
• Smoking cessation