| Patho | Autoimmune vs. Gliadin (HLA-DQ2/8) | Transmural inflammation (Th1 mediated) | Post-infectious; affects entire small bowel | Lactase enzyme deficiency | Gut-brain axis d/o; visceral hypersensitivity |
| Location | Proximal Small Bowel (Duodenum) | Anywhere (“mouth to anus”); Terminal Ileum common | Entire Small Bowel | Small Intestine Brush Border | Colon (Function, not structure) |
| Biopsy | Villous atrophy, crypt hyperplasia | Non-caseating granulomas, transmural inflammation | Villous atrophy (less severe) | Normal | Normal |
| KeyDx | ↑ Anti-tTG Ab; Dermatitis herpetiformis | Skip lesions, “cobblestoning”, fistulas | Hx of travel to tropics; Folate/B12 def. | H₂ breath test; symptoms with dairy | Pain relieved by defecation; Dx of exclusion |
| Tx | Gluten-free diet | Anti-TNF, Corticosteroids, 5-ASA | Antibiotics, Folic Acid | Avoid dairy; lactase pills | Low FODMAP diet, fiber, symptom control |