A 25-year-old man presents with chronic diarrhea, steatorrhea, and weight loss for 3 years. Duodenal biopsy shows total villous atrophy (Marsh IIIc), crypt hyperplasia, and intraepithelial lymphocytosis. Anti-tissue transglutaminase IgA is strongly positive. Despite 12 months of strict gluten-free diet, he shows no histological improvement. What is the next most important investigation?

• A Repeat anti-tTG IgA to assess dietary compliance
• B Capsule endoscopy and deep small bowel biopsies to exclude refractory celiac disease or enteropathy-associated T-cell lymphoma (EATL) ✓
• C HLA DQ2/DQ8 typing to confirm genetic susceptibility
• D Trial of budesonide for presumed refractory celiac disease type 1

Explanation

Non-response to strict gluten-free diet after 12 months in a confirmed celiac patient raises concern for refractory celiac disease (RCD) or the development of enteropathy-associated T-cell lymphoma (EATL), which is a rare but serious complication. Capsule endoscopy and deep enteroscopy with biopsies from affected segments are essential to identify ulcerative jejunitis, EATL, or aberrant intraepithelial T-cell clones (characteristic of RCD type II). Flow cytometry of IELs looking for aberrant CD3+CD8–CD103– T-cell population distinguishes RCD type II from type I.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.