Derm Cases · Dermatology / Immunobullous / Coeliac disease
OSCE — intensely pruritic extensor vesicles: diagnose and manage dermatitis herpetiformis
An 8-minute OSCE station on recognising dermatitis herpetiformis, ordering perilesional DIF and coeliac serology, starting a gluten-free diet, and using dapsone only after G6PD screening with appropriate monitoring.
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NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on recognising dermatitis herpetiformis, ordering perilesional DIF and coeliac serology, starting a gluten-free diet, and using dapsone only after G6PD screening with appropriate monitoring.
Brief (to candidate)
A 32-year-old man has months of intense itching with grouped excoriated papulovesicles on the elbows, knees, buttocks and scalp. He denies diarrhoea but has mild iron deficiency. No bullae on examination — only scratched residual papules. You have 8 minutes to diagnose dermatitis herpetiformis, plan confirmation tests, link to coeliac disease, and start safe first-line therapy.
[1]Candidate instructions
- Recognise the classic distribution and symptom severity.
- Order the correct biopsy site and immunofluorescence study.
- Screen for coeliac disease and related autoimmunity.
- Counsel a lifelong gluten-free diet.
- Prescribe dapsone only after G6PD check and list monitoring.
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Recognition | Intensely pruritic grouped papulovesicles/excoriations on extensors (elbows, knees, buttocks, scalp, shoulders); primary vesicles often destroyed by scratching[1][3] |
| Pathology confirmation | Perilesional skin for DIF: granular IgA at dermal papillae tips; lesional H&E may show papillary dermal neutrophilic microabscesses — do not biopsy only a scratched crust without DIF plan |
| Coeliac link | Virtually all DH has gluten-sensitive enteropathy (often subclinical); serology (tTG-IgA, total IgA, endomysial IgA as indicated); GI referral/endoscopy per local coeliac pathways; HLA-DQ2/DQ8 context when helpful[2] |
| Diet | Lifelong gluten-free diet is disease-modifying therapy for skin and gut; explains slow cutaneous lag vs rapid dapsone itch relief |
| Dapsone safety | Check G6PD before start; warn haemolysis, methaemoglobinaemia, dapsone hypersensitivity; monitor FBC (and methaemoglobin if symptomatic); dose titration for itch control then taper once diet established |
| Differentials | Scabies, eczema, linear IgA, bullous pemphigoid, neurotic excoriations — DIF and coeliac work-up separate DH |
| Safety-net | Screen associated autoimmune disease risk (thyroid); dietary dietitian support; do not start dapsone without G6PD |
Model key actions
- Suspect DH from extensor pruritic grouped lesions; confirm with perilesional DIF granular IgA.[1][3]
- Investigate and manage as coeliac disease with lifelong gluten-free diet.[2]
- Use dapsone after G6PD screening for rapid itch control while diet takes effect.
Common errors
- Biopsying only a crusted lesion without DIF.
- Treating as eczema/scabies without coeliac work-up.
- Starting dapsone without G6PD check.
- Saying diet is optional once dapsone controls itch.
- Missing that GI symptoms may be absent yet enteropathy still present.
References3ShowHide
- [1]Salmi TT. Dermatitis herpetiformis. Clinical and experimental dermatology, 2019.PMID 31093998
- [2]Al-Toma A, Volta U, Auricchio R, et al. European Society for the Study of Coeliac Disease (ESsCD) guideline for coeliac disease and other gluten-related disorders. United European gastroenterology journal, 2019.PMID 31210940
- [3]Reunala T, Hervonen K, Salmi T. Dermatitis Herpetiformis: An Update on Diagnosis and Management. American Journal of Clinical Dermatology, 2021.PMID 33432477