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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Cutaneous manifestation of coeliac disease — nearly ALL have underlying enteropathy
- Intensely pruritic grouped vesicles on extensor surfaces: elbows, knees, buttocks, scalp
- DIF: GRANULAR IgA at dermal papillae — distinguishes from linear IgA disease and BP
- Treatment: strict lifelong GLUTEN-FREE DIET. Dapsone for rapid symptom control
- Check G6PD before dapsone. Screen with anti-tTG IgA. Consider duodenal biopsy
Overview
Dermatitis herpetiformis (DH) is the cutaneous manifestation of coeliac disease. IgA antibodies against epidermal transglutaminase deposit in dermal papillae. Despite its name, unrelated to herpes — refers to the herpetiform (grouped) vesicle arrangement. ~90-100% have coeliac enteropathy on biopsy (though GI symptoms may be absent). Both skin and gut disease are gluten-driven.
Epidemiology
Prevalence ~10-40 per 100,000. Male:female ~2:1. Peak 30-40 years. HLA-DQ2 (90%) and HLA-DQ8 (5%). Same long-term risks as coeliac: osteoporosis, nutritional deficiencies, GI lymphoma risk (reduced by GFD).
Clinical Features
Symptoms
Intensely pruritic grouped small vesicles/papules on extensor surfaces symmetrically
Elbows, knees, buttocks, shoulders, scalp, sacrum
Often excoriated by presentation — may only see crusted papules
GI symptoms may be absent or mild
Signs
Grouped small vesicles and excoriations on extensors
Vesicles fragile — often excoriated
Investigations
First-line
DIF (perilesional skin)GRANULAR IgA at dermal papillae — DIAGNOSTIC
Anti-tTG IgAPositive in ~70-90% — supports coeliac diagnosis
Second-line
Anti-EMAMore specific than tTG
Total serum IgACheck for IgA deficiency — false negatives
Specialist
Duodenal biopsyVillous atrophy confirms coeliac enteropathy
G6PD levelBEFORE dapsone — dapsone causes haemolysis, severe in G6PD deficiency
Management
BAD Guidelines + BSG Coeliac Guidelines1
Gluten-free diet (lifelong)
- Treats both skin and gut disease
- Skin response takes 6-24 months
- Dietitian referral
- Reduces GI lymphoma and osteoporosis risk
2
Dapsone (rapid symptom control)
- Dapsone 50-150 mg OD — controls itch within days
- Check G6PD BEFORE starting
- Monitor FBC regularly (haemolysis, methaemoglobinaemia)
- Taper and stop once GFD controls disease (6-24 months)
Complications
- Same as coeliac: Iron/folate deficiency, osteoporosis, splenic atrophy, EATL lymphoma
- Dapsone side effects: Dose-dependent haemolysis, peripheral neuropathy
UKMLA Exam Tips
- 1DH = GRANULAR IgA. Linear IgA disease = LINEAR IgA. BP = LINEAR IgG/C3
- 2Nearly ALL have coeliac enteropathy — even if GI asymptomatic
- 3Check G6PD before dapsone — risk of severe haemolysis
- 4EXTENSOR vesicles + intense itch + coeliac serology = DH
- 5"Herpetiform" means grouped — NOTHING to do with herpes viruses
- 6GFD is DEFINITIVE treatment. Dapsone is a bridge
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