Exuberant Dermatitis Herpetiformis With Oral Involvement Mimicking Behçet Disease and Disseminated Herpetic Infection: The Crucial Role of Direct Immunofluorescence.

Dermatitis herpetiformis (DH) is a chronic autoimmune blistering dermatosis associated with gluten-sensitive enteropathy and characterized by intensely pruritic papulovesicular eruptions, typically distributed symmetrically on extensor surfaces. Although DH classically presents with grouped vesicles and excoriated papules, atypical and exuberant manifestations may represent a substantial diagnostic challenge, frequently mimicking infectious, inflammatory, and autoimmune blistering disorders. We report the case of a 30-year-old woman presenting with a one-year history of progressive, intensely pruritic vesiculobullous and erosive lesions involving the trunk and extremities, accompanied by painful oral ulcerations, hemorrhagic crusts, extensive excoriations, secondary bacterial infection, and diffuse post-inflammatory hyperpigmentation. The patient was initially diagnosed with Behçet disease and subsequently hospitalized for suspected disseminated herpetic infection, receiving systemic corticosteroids and intravenous acyclovir without significant clinical improvement. Dermatological examination revealed widespread erosive and vesiculobullous lesions associated with severe inflammatory activity and oral aphthoid ulcerations. Histopathological examination of active lesions demonstrated intraepidermal blister formation associated with eosinophilic infiltrate and scattered acantholytic cells, findings that initially suggested alternative autoimmune blistering disorders. Direct immunofluorescence (DIF) demonstrated characteristic granular IgA deposition predominantly localized at the tips of dermal papillae, confirming the diagnosis of DH despite atypical histopathological findings. Serological evaluation further revealed positive anti-tissue transglutaminase and anti-endomysial antibodies, corroborating the diagnosis. Treatment with dapsone combined with a strict gluten-free diet resulted in marked clinical improvement. This case highlights the importance of clinicopathological and immunopathological correlation in atypical presentations of autoimmune blistering diseases and underscores the essential role of DIF in establishing the diagnosis of DH.