What are the causes of microscopic colitis?

Causes of Microscopic Colitis

Microscopic colitis is primarily triggered by medications (especially NSAIDs, PPIs, SSRIs, and statins), autoimmune conditions, and possibly certain gastrointestinal infections in genetically susceptible individuals. 1

Key Etiological Factors

Medication-Induced Causes

• Medications are well-established triggers and should be thoroughly evaluated in all patients:

  • NSAIDs: Strongly associated with both collagenous and lymphocytic colitis 1, 2
  • Proton Pump Inhibitors (PPIs): Significant trigger with up to 3.37-fold increased risk 1, 3
  • Selective Serotonin Reuptake Inhibitors (SSRIs): Particularly sertraline, with 2.03-fold increased risk 1, 3
  • Statins: Identified as potential triggers in some studies 1, 2

• Combined medication use carries even higher risk:

  • Concomitant use of PPIs and NSAIDs shows the strongest association with a fivefold increased risk 3
  • Prolonged use (4-12 months) further increases risk compared to shorter exposure 3

Autoimmune and Associated Conditions

• Autoimmune diseases are commonly associated with microscopic colitis:

  • Rheumatic diseases 1
  • Thyroid disorders 1
  • Celiac disease: Present in 5-7% of microscopic colitis patients 1, 4

• Bile acid malabsorption:

  • Present in 41% of collagenous colitis cases 5, 1
  • Present in 29% of lymphocytic colitis cases 5, 1

Infectious Triggers

• Enteric infections may trigger disease onset or exacerbate symptoms 5, 1
• Post-infectious irritable bowel syndrome can present similarly 5
• Specific pathogens implicated include:
  • Clostridium difficile 5
  • Campylobacter species 5
  • Spirochaetosis 5

Host Factors

• Demographic risk factors:

  • Female sex: Women make up 77% of collagenous colitis and 68% of lymphocytic colitis cases 5, 1
  • Age: Mean age at presentation is around 60 years, though 25% of cases occur in patients under 45 5, 1

• Lifestyle factors:

  • Cigarette smoking 1
  • Alcohol consumption 1

Pathophysiological Mechanisms

The pathogenesis of microscopic colitis is multifactorial and likely involves:

1. Medication-induced inflammation:

   • NSAIDs may cause direct mucosal injury 2, 3
   • PPIs may alter intestinal microbiota (dysbiosis) 3

2. Immune dysregulation:

   • Abnormal immune response to luminal antigens in susceptible individuals 5
   • Represents a specific mucosal response to various noxious agents 5

3. Altered intestinal permeability:

   • May be exacerbated by NSAID-related side effects 3
   • Potentially worsened by PPI-induced dysbiosis 3

Clinical Implications

• Medication review is essential in all patients with microscopic colitis
• Consider discontinuation of potential trigger medications when possible 1, 6
• Screen for associated conditions (celiac disease, bile acid diarrhea) 1
• In refractory cases, consider immunosuppressive therapy for underlying immune dysregulation 1, 4

Common Pitfalls to Avoid

• Failing to obtain biopsies from multiple segments of the colon during diagnosis 1
• Overlooking associated conditions like celiac disease in patients with persistent symptoms 1
• Continuing potential medication triggers in patients with refractory symptoms 1, 6

Understanding these etiological factors is crucial for effective management, as treatment should target the underlying cause whenever possible.