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Dermatitis herpetiformis
Dermatitis herpetiformis is the skin manifestation of coeliac disease: small, intensely itchy grouped blisters on the elbows, knees and buttocks, with granular IgA deposits in the dermal papillae, responding to dapsone and a gluten-free diet.
Why it matters in the exam
The classic stem shows a young adult with intense itch and excoriated lesions on the elbows, knees and buttocks who arrives with "eczema that does not respond". The question turns on diagnosis (biopsy of normal-looking skin next to a lesion for DIF), the associated test (anti-transglutaminase antibodies), treatment (dapsone for rapid relief and a gluten-free diet long term) and the test before dapsone — G6PD level. Remember that most patients do not complain of diarrhoea, yet small-bowel biopsy often shows coeliac damage, and that a gluten-free diet also lowers the risk of intestinal lymphoma. The disease is linked to HLA-DQ2 and DQ8 and to other autoimmune diseases such as thyroid disease, so thyroid function is worth checking as well. Remember too that skin improvement on diet alone is slow and takes many months, so dapsone is combined at first and tapered as the diet takes effect.
Key points
- Dermatitis herpetiformis is the skin manifestation of coeliac disease and presents with small, intensely itchy blisters on extensor surfaces and the buttocks.
- The diagnostic test is DIF of nearby normal skin, showing granular IgA at the tips of the papillae.
- Most patients have small-bowel damage even without gastrointestinal symptoms.
- Dapsone relieves itch quickly but needs a G6PD test before starting and monitoring for haemolysis and methaemoglobinaemia.
- A lifelong gluten-free diet is the basic treatment, reducing the need for dapsone and the risk of lymphoma.
Summary table
| Aspect | Finding | Meaning | Action |
|---|---|---|---|
| Clinical | Small grouped vesicles and papules, excoriations, on the elbows, knees, buttocks and scalp | Very intense itch; blisters are scratched and usually look like erosions | Suspect it even when the patient "only itches" |
| Direct immunofluorescence | Granular IgA at the tips of the dermal papillae | Gold standard for diagnosis | Biopsy normal skin next to a lesion |
| Serology | IgA antibodies against epidermal and tissue transglutaminase | Supports the diagnosis and the link to coeliac disease | Check total IgA to exclude IgA deficiency |
| Gut | Villous damage in most patients, often without symptoms | Subclinical coeliac disease | Intestinal lymphoma risk falls with diet |
| Treatment | Dapsone relieves itch within days; lifelong gluten-free diet | Dapsone does not treat the gut | Check G6PD before dapsone; monitor blood count and methaemoglobinaemia |
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Sources
- British Society of Gastroenterology guidelines on the diagnosis and management of coeliac disease, 2014 — Dermatitis herpetiformis
- European Society for the Study of Coeliac Disease guideline, 2019 — Extra-intestinal manifestations
- S2K guideline on diagnosis and treatment of dermatitis herpetiformis (EADV), 2021 — Diagnosis and treatment
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.