Clinical meaning
Dermatitis herpetiformis (DH) is a chronic autoimmune blistering skin disease that represents the cutaneous manifestation of celiac disease (gluten-sensitive enteropathy). Nearly 100% of DH patients have underlying celiac disease on intestinal biopsy, though most are asymptomatic from a GI standpoint. The pathogenesis begins with ingestion of gluten (gliadin peptides from wheat, barley, and rye). In genetically susceptible individuals (HLA-DQ2 or HLA-DQ8), tissue transglutaminase (tTG) deamidates gliadin peptides in the gut mucosa, creating immunogenic epitopes that trigger T-cell-mediated intestinal inflammation (villous atrophy characteristic of celiac disease). Simultaneously, the immune response generates IgA antibodies against tissue transglutaminase (anti-tTG) and its skin-specific isoform, epidermal transglutaminase (eTG). These IgA-eTG immune complexes deposit at the dermal papillae of the skin, activating complement and recruiting neutrophils, producing the characteristic granular IgA deposits visible on direct immunofluorescence (DIF) — the gold standard diagnostic test. The neutrophilic infiltration causes microabscesses at the dermal papillae, leading to subepidermal vesicle formation. Clinically, DH presents as intensely pruritic grouped vesicles and papulovesicles on extensor surfaces (elbows, knees, buttocks, posterior scalp, upper back). The itch is so intense that patients typically excorate...