GI NOTES

Celiac Disease

1. Who to test

Group	Examples
GI symptoms	Chronic diarrhea, bloating, weight loss, abdominal pain, constipation
Non-GI clues	Iron deficiency anemia, raised transaminases, osteoporosis or osteopenia, dermatitis herpetiformis, infertility, peripheral neuropathy, dental enamel defects
Higher-risk groups	First-degree relatives, type 1 diabetes, autoimmune thyroid disease, Down or Turner syndrome, selective IgA deficiency

2. Diagnosis

• Histology (Marsh classification): intraepithelial lymphocytosis, crypt hyperplasia, villous atrophy. Similar changes can be caused by olmesartan, tropical sprue, common variable immunodeficiency, giardiasis, Crohn disease and others.
• HLA-DQ2/DQ8 typing is useful to rule out celiac disease when negative (very high negative predictive value), for example in someone already on a gluten-free diet.
• Gluten challenge if already gluten-free: about 3 to 10 g of gluten a day (roughly 2 slices of bread) for several weeks before serology and biopsy.
• In children, a biopsy-free diagnosis is possible when tTG-IgA is 10 or more times the upper limit with a positive endomysial antibody. In adults, biopsy confirmation remains standard.

3. Management

• Strict gluten-free diet for life: no wheat, barley or rye. Pure oats are tolerated by most patients. Refer to an experienced dietitian.
• At diagnosis, check: iron, folate, vitamin B12, vitamin D, zinc, copper, liver tests. Consider bone density testing in adults, especially with risk factors.
• Vaccines: pneumococcal vaccine because of possible hyposplenism.
• Screen first-degree relatives.

Follow-up

When	What
3 to 6 months	Symptoms, diet review with dietitian, tTG-IgA
6 to 12 months	tTG-IgA should be falling or normal; repeat labs for deficiencies
Yearly after that	Symptoms, adherence, tTG-IgA, labs as needed
Persistent symptoms or positive serology	Review for gluten exposure; consider repeat duodenal biopsy

4. Non-responsive celiac disease

1. Confirm the original diagnosis (serology and histology were truly consistent).
2. Look for gluten exposure, the most common cause, with a dietitian.
3. Consider other causes: microscopic colitis, small intestinal bacterial overgrowth, pancreatic insufficiency, lactose or fructose intolerance, IBS, IBD.
4. Refractory celiac disease: persistent villous atrophy despite at least 12 months of a strict diet. Type II carries a risk of enteropathy-associated T-cell lymphoma; refer to a specialist center.

5. High-yield pearls

• Do not start a gluten-free diet before testing; it makes serology and biopsy falsely negative.
• Always check total IgA; about 2 to 3% of celiac patients are IgA deficient.
• Dermatitis herpetiformis (itchy blisters on elbows, knees, buttocks) is celiac disease of the skin; skin biopsy can confirm it.
• Unexplained iron deficiency in an adult without bleeding should prompt celiac testing.

References

• Rubio-Tapia A, Hill ID, Semrad C, et al. American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease. Am J Gastroenterol. 2023;118(1):59-76.
• Husby S, Koletzko S, Korponay-Szabo I, et al. European Society Paediatric Gastroenterology, Hepatology and Nutrition Guidelines for Diagnosing Coeliac Disease 2020. J Pediatr Gastroenterol Nutr. 2020;70(1):141-156.
• Al-Toma A, Volta U, Auricchio R, et al. European Society for the Study of Coeliac Disease (ESsCD) guideline for coeliac disease and other gluten-related disorders. United European Gastroenterol J. 2019;7(5):583-613.

For educational purposes only. This note does not replace clinical judgment or local protocols. Check doses against current labeling and institutional guidance.