A 45-year-old woman presents with chronic diarrhoea, weight loss, and an itchy blistering skin rash on the elbows and buttocks. Anti-tissue transglutaminase (anti-tTG) IgA is markedly elevated. Duodenal biopsy shows villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis (Marsh grade 3b). The skin rash is most consistent with:

• A Linear IgA bullous dermatosis
• B Bullous pemphigoid
• C Dermatitis herpetiformis (Duhring's disease) ✓
• D Erythema multiforme

Explanation

Dermatitis herpetiformis (DH) is the cutaneous manifestation of coeliac disease, presenting with intensely pruritic vesicular lesions on extensor surfaces (elbows, knees, buttocks). Direct immunofluorescence shows granular IgA deposits at the dermo-epidermal junction. It is associated with high anti-tTG IgA and Marsh grade 3 duodenal changes in virtually all cases. Linear IgA disease shows linear IgA on DIF. Bullous pemphigoid involves IgG at the basement membrane.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.