CELIAC DISEASE

I. Epidemiology

1. Prevalance: Higher than previously thought, probably About 1:120-300 in Europe & North America
2. Risk is increased in patients with the following conditions:
   1. Autoimmune thyroid disease
   2. Dermatitis herpetiformis
   3. Type 1 diabetes
   4. First-degree relative with type 1 diabetes or celiac disease

II. Pathophysiology

1. Autoimmune process in small intestine
2. Triggered by ingestion of gluten (mostly from grain products, including wheat, rye, and barley, but not oats, rice, or corn)
3. Abnormal T-cell response results in antibodies against intestinal tissues
4. Risk may be related to age at first dietary gluten exposure
   1. Incidence of was sig. higher in children first exposed to gluten at < 3 months of age (HR 23) or at > 7 months of age (HR 4) compared with first exposure at 4-6 months of age, in an observational study of 1,560 children at increased risk for caliac disease (as defined by having HLA-DR3 or -DR4 alleles) followed for mean 4.8y (JAMA 293:2343, 2005--abst)

III. Clinical features

1. "Classic" presentation is in infancy with diarrhea and failure to thrive but about 20% of cases occur in pts > 60yo
2. Typical symptoms
   1. Diarrhea
   2. Flatulence
   3. Weight loss
   4. Fatigue
   5. Anemia (from iron deficiency and/or folate malabsorption)
   6. Coagulopathy (from vit. K deficiency)
   7. Hypocalcemia and osteoporosis (from malabsorption of vit. D)
3. Risk of malignancy in patients with celiac disease
   1. In population studies (e.g. BMJ 329:716, 2004--JW), increased risk of intestinal T-cell lymphoma has been observed
   2. In one retrospective population study of pts with celiac antibodies, overall indicence of malignancy was not elevated compared to the general population, but among those positive for endomyseal antibodies, risk for lymphoproliferative disease was sig. elevated (RR 6.43) (Gut 58:643, 2009-JW)

IV. Diagnosis

1. Sensitivity of serologic testing is reduced if pt does not have gluten in their diet
2. Anti-tissue transglutaminase IgA (first-line serologic test)
   1. Anti-tissue transglutaminase Ab testing, compared with small-bowel biopsy, had a sensitivity of 70.6% and specificity of 65.0% for celiac disease in one series of 122 pts with suspected celiac disease, all of whom underwent testing with both (Clin. Gastroent. Hepatol. 4:726, 2006--JW)
   2. Had sensitivity of 89% and specificity of 98% in one meta-analysis (JAMA 303:1738, 2010-abst)
3. IgA anti-endomysial and anti-gliadin antibodies (if anti-tissue transglutaminase IgA is equivocal)
   1. IgA antiendomysial Ab had sensitivity of 90% and specificity of 99% in one meta-analysis (JAMA 303:1738, 2010-abst)
4. Endomysial Ag
5. Endoscopic bx of distal duodenum
   1. "Gold standard" as of 2009
   2. However, for children with positive serologic tests for celiac disease but normal villous structure on small-bowel biopsy, and symptoms suggestive of celiac disease (e.g. abdominal pain, diarrhea, poor growth), there was some evidence of benefit from gluten-free diet in nonrandomized studies (J. Pediat. 157:373, 2010-JW)

V. Treatment

1. Gluten-free diet usually produces significant improvement within weeks, though histologic abnormalities in small intestine may persist
2. When diet alone is insufficient (rare), Corticosteroids and other immunosuppressants have been used