Which serologic test is most specific for detecting celiac disease in the setting of dermatitis herpetiformis?

• A. Anti-gliadin antibodies
• B. Endomysial antibodies
• C. IgA anti-tissue transglutaminase antibodies
• D. Anti-neutrophil cytoplasmic antibodies

Answer: (C)

In dermatitis herpetiformis, which is a skin manifestation of gluten-sensitive enteropathy, the immune response to gluten is often detected with antibodies against tissue transglutaminase. The IgA anti-tTG test is the most specific serologic marker for celiac disease and is widely used because it closely reflects the underlying autoimmune process and correlates with intestinal damage. Anti-gliadin antibodies are older and less specific, endomysial antibodies are highly specific but more technically demanding and less practical as a routine first test, and anti-neutrophil cytoplasmic antibodies are unrelated to celiac disease. Therefore, IgA anti-tTG offers the best combination of specificity and practicality for confirming celiac disease in patients with dermatitis herpetiformis. If IgA deficiency is possible, total IgA should be checked and alternative IgG-based tests considered.