What does a finding of increased intra‑epithelial T‑lymphocytes on colonoscopic biopsy indicate and how should it be managed?

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Increased Intraepithelial T-Lymphocytes on Colonoscopy

When colonoscopic biopsy reveals increased intraepithelial lymphocytes (IELs), the primary concern is celiac disease, which must be excluded first through serologic testing (IgA tissue transglutaminase with total IgA level), followed by systematic evaluation for microscopic colitis, medications, and other causes if celiac serology is negative.

Diagnostic Threshold and Initial Interpretation

The finding of increased colonic IELs is defined as ≥20 intraepithelial lymphocytes per 100 colonocytes 1. This is distinct from duodenal IEL counts, where ≥25 IELs per 100 enterocytes is the threshold 2.

Systematic Diagnostic Approach

Step 1: Rule Out Celiac Disease First

Celiac disease is the most critical diagnosis to exclude, particularly in lymphocytic colitis where approximately one-third of patients may have concurrent celiac disease 1. The association is stronger for lymphocytic colitis than collagenous colitis.

  • Order IgA tissue transglutaminase (IgA-TG2) with total serum IgA level 2, 3
  • If IgA deficient (occurs in 1-3% of celiac patients vs 1 in 500 general population), order IgG-based testing: IgG-TG2 and IgG-DGP 2, 4
  • Consider IgA endomysial antibody (EMA) for confirmation if tTG is positive 2
  • If serology is positive, refer to gastroenterology for upper endoscopy with duodenal biopsies to confirm villous atrophy 3

Critical pitfall: Even with colonic findings, celiac disease primarily affects the duodenum, so upper endoscopy is mandatory for diagnosis 2.

Step 2: Evaluate for Microscopic Colitis

If celiac serology is negative, the differential focuses on lymphocytic colitis versus collagenous colitis 1, 5:

Lymphocytic colitis features:

  • Diffuse increase of IELs (>20 per 100 epithelial cells) in surface epithelium
  • Increased lamina propria inflammatory cells
  • No thickening of subepithelial collagen band 1

Collagenous colitis features:

  • Same IEL increase as lymphocytic colitis
  • Thickened subepithelial collagen band (>10 μm) 1, 5
  • May require trichrome stain or Tenascin immunohistochemistry to confirm collagen deposition 1

Both conditions:

  • Affect women more (77% collagenous, 68% lymphocytic)
  • Mean age ~60 years, but 25% present under age 45 5
  • Associated with autoimmune diseases (rheumatic, thyroid), celiac disease (5-7%), and bile acid diarrhea (41% collagenous, 29% lymphocytic) 5

Step 3: Medication Review

Key medications causing colonic IEL increase 2:

  • NSAIDs
  • Olmesartan
  • Mycophenolate mofetil
  • Chemotherapy agents

Step 4: Consider Other Etiologies

If above workup is negative, evaluate for 2:

Autoimmune conditions:

  • Autoimmune enteropathy (especially pediatric patients) 6
  • Rheumatoid arthritis, Sjögren's syndrome, thyroid disease
  • Type 1 diabetes mellitus

Infections:

  • Giardiasis
  • Post-infectious diarrhea
  • HIV enteropathy
  • Cryptosporidium

Other causes:

  • Small intestinal bacterial overgrowth
  • Inflammatory bowel disease (particularly if architectural changes present) 6
  • Common variable immunodeficiency

Management Algorithm

If Celiac Disease Confirmed:

  • Strict lifelong gluten-free diet 2, 3
  • Consultation with registered dietitian experienced in both diabetes (if applicable) and celiac disease 3
  • Monitor for response with repeat serology and consider repeat biopsy if non-responsive 7

If Microscopic Colitis Diagnosed:

  • Consider bile acid sequestrant trial (cholestyramine or colesevelam) given high prevalence of concurrent bile acid diarrhea 5
  • Budesonide for refractory cases
  • Screen for celiac disease given 5-7% association 5

If Medication-Related:

  • Discontinue offending agent if possible
  • Repeat colonoscopy with biopsies after appropriate washout period to confirm resolution

Critical Warnings

  1. Do not diagnose seronegative celiac disease without villous atrophy - increased IELs alone with normal villi does not constitute celiac disease or seronegative enteropathy 4

  2. Pediatric patients with colonic IEL plus architectural/inflammatory changes: Consider inflammatory bowel disease strongly 6

  3. Refractory symptoms despite treatment: Consider refractory celiac disease subtypes using flow cytometry, immunohistochemistry, and T-cell receptor rearrangement studies to exclude enteropathy-associated T-cell lymphoma 7

  4. Terminal ileum involvement: May occur in microscopic colitis; consider obtaining terminal ileum biopsies during colonoscopy 1

References

6
Research

Clinical significance of colonic intraepithelial lymphocytosis in a pediatric population.

Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc, 2009

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.