Microscopic Colitis

 

Common sites:

    • 50’s and 60’s peak incidence
      • Rare in children
    • F>M (~2.5:1)
    • Unknown etiology
    • Associated with autoimmune diseases:
      • Thyroiditis (19%)
      • Rheumatoid arthritis (4%)
      • Fibromyalgia
      • Celiac (up to 30%, but often does not respond to Gluten-free diet)
      • Lymphocytic gastritis
      • “lymphocytic gastroenterocolitis”
    • Drugs associated:
      • Ranitidine ruscus extract (Cyclo 3 Fort)
      • PPIs
      • B-adrenergic receptor blockers
      • Statins
      • Bisphosphonates
      • SSRIs
      • Ipilimumab
      • others

 

Gross features:

    • Normal endoscopy almost by definition
      • May show mild erythema, congestion, and decreased vascular markings
      • Rarely ulceration caused by coexisting infection / drug reactions
    • Diffuse or patchy distribution

 

Histologic features:

    • Collagenous colitis:
      • Collagen membrane below epithelium (at least 2 RBC’s thick)
      • Lymphocytosis (+)
      • Dense chronic inflammatory infiltrate in lamina propria (+)
      • Crowded crypts (++)
    • Lymphocytic colitis:
      • No collagen membrane
      • Lymphocytosis (+++) (>20 lymphocytes per 100 epithelial cells)
        • Count in the surface epithelium between the crypts
      • Epithelial cell injury:
        • Epithelial degeneration
        • Mucin depletion
        • Cuboidal shape / flattening
        • Cytoplasmic basophilia / hypereosinophilia
        • Nuclear stratification
      • Crypt architecture normal or near normal
        • Crowded crypts (++)
      • Dense chronic inflammatory infiltrate in superficial lamina propria (++)
        • Lymphocytes and plasma cells
        • Eosinophils absent or few (contrast to collagenous colitis)
      • IBD features usually absent
        • Focal / mild if present
      • “paucicellular” or “minimal change” lymphocytic colitis:
        • Minimal histologic changes
        • Only slight increase in intraepithelial lymphocytes (7 to 20 per 100 ep cells)
        • Minimal epithelial changes or absent

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 

 

 

 

Molecular features:

    •  

 

Other features:

    • Chronic watery, non-bloody diarrhea
    • Other abdo / GI symptoms (but typically not n/v)
    • Wt. loss (up to 48%)
    • Normal physical exam
    • Normal routine lab tests
    • Normal scope findings
    • DDx:
      • IBD
      • Infectious colitis
      • Diverticular disease
      • Enteropathy-associated T-cell lymphoma (EATL)
      • Autoimmune enteropathy (especially in pediatric patients)
    • Spontaneous resolution in 18%
    • Salicylates (mesalazine) and budesonide therapy can cause remission in 86% of patients
      • May relapse (25-44%)

 

References:

    • Odze and Goldblum (2015)