For dermatitis herpetiformis with suspected celiac disease, which combination of tests best supports the diagnosis?

• A. Skin biopsy with direct immunofluorescence, positive serology for IgA TTG, and duodenal biopsy showing villous atrophy
• B. Skin biopsy alone
• C. Skin biopsy plus imaging only
• D. Serology alone

Answer: (A)

The key idea is that dermatitis herpetiformis is a gluten-sensitive condition that affects both the skin and the gut, so confirming the diagnosis involves evidence from skin, serology, and intestinal tissue. Perilesional skin biopsy with direct immunofluorescence shows granular IgA deposits in the dermal papillae, which is the characteristic skin finding in dermatitis herpetiformis. To tie this to celiac disease, serology for IgA anti-tissue transglutaminase antibodies provides a sensitive test for gluten-sensitive enteropathy. Finally, a duodenal biopsy showing villous atrophy demonstrates the intestinal involvement typical of celiac disease. Together, these three pieces—skin immunofluorescence positivity, supportive serology, and compatible duodenal histology—confirm the diagnosis more robustly than any single test alone.

Skin biopsy alone would confirm the skin manifestation but not the associated enteropathy. Adding imaging doesn’t provide the immune or mucosal evidence needed. Serology alone supports celiac disease but does not demonstrate the characteristic skin pathology or gut histology.