Dermatitis herpetiformis is best characterized by which immunofluorescence finding?

• A. Granular deposition of IgA at the dermal papillae
• B. Linear deposition of IgG along the basement membrane
• C. Granulomatous inflammation
• D. Subepidermal blister with eosinophils

Answer: (A)

The key idea here is the immunofluorescence pattern that specifically identifies dermatitis herpetiformis. In this condition, immune complexes of IgA deposit in the dermal papillae, forming granular (not linear) IgA staining at the tips of the dermal papillae on direct immunofluorescence. This granular IgA at the dermal papillae is the hallmark finding and helps distinguish DH from other blistering diseases.

For context, dermatitis herpetiformis is strongly associated with gluten sensitivity and often with celiac disease. The IgA deposits correlate with antibodies directed against epidermal transglutaminase, and they drive neutrophilic microabscesses in the papillary dermis that underlie the itchy vesicles.

The other patterns described are seen in different diseases: linear IgG along the basement membrane is typical of bullous pemphigoid; granulomatous inflammation is a histologic pattern, not an immunofluorescence finding; and a subepidermal blister with eosinophils points to other subepidermal blistering diseases, not the granular IgA deposition characteristic of dermatitis herpetiformis.