Dermatitis herpetiformis — diagnosis and safe management

Stem

A 28-year-old man has six months of severe itch, excoriated grouped papules, and occasional tiny vesicles over both elbows, knees, and buttocks. He reports bloating but no weight loss or diarrhoea. His sister has coeliac disease. ^[1][2]

Questions and model answer

a) Give the diagnosis and two clinical clues. (2 marks)

• Diagnosis: dermatitis herpetiformis (DH).
• Clues: intensely pruritic, symmetrical grouped papulovesicles/excoriations on extensor surfaces; and the coeliac association/family history. Gastrointestinal symptoms may be absent. ^[1][2]

b) How will you confirm DH and assess associated coeliac disease? (3 marks)

1. Diagnostic test: direct immunofluorescence (DIF) of normal-appearing perilesional skin, sent in the laboratory-approved immunofluorescence medium and not formalin. The characteristic finding is granular IgA in the papillary dermis and/or dermoepidermal junction. ^[2][3]
2. Supportive test: a separate fresh lesional biopsy in formalin for H&E may show papillary neutrophilic microabscesses and a neutrophil-rich subepidermal blister; histology is supportive, not independently diagnostic. ^[2]
3. Coeliac assessment: IgA anti-TG2 with total IgA while eating gluten; use an IgG-based pathway if IgA deficient. Anti-TG3 may support DH when available. Assess symptoms, nutrition, and documented deficiencies. A duodenal biopsy is not routine solely because DIF-confirmed DH is present; reserve it for uncertainty, severe/incongruent gastrointestinal features, or suspected complications. ^[1][2]

c) Outline definitive treatment and safe rapid symptom control. (3 marks)

• Definitive therapy: strict lifelong gluten-free diet with a specialist dietitian. Skin control is slow; full remission and dapsone withdrawal average about two years, not a guaranteed 6–12 months. ^[1][2]
• Rapid control: if symptoms warrant it, start oral dapsone 25–50 mg once daily, then titrate gradually toward 100 mg daily only if needed, using the lowest effective dose. Itch often improves within hours to days, but dapsone does not treat the enteropathy. ^[1][2][3]
• Before dapsone: CBC with differential, G6PD activity, liver function, and renal function. Normal G6PD activity does not remove dose-related haemolysis or methaemoglobinaemia risk. ^[2]

d) State the monitoring and long-term follow-up principles. (2 marks)

• Use a local dapsone protocol. One published schedule checks CBC weekly in month 1, every two weeks for the next eight weeks, then every 3–4 months; liver tests are checked every two weeks in month 1 and then every 3–4 months with renal function. Check reticulocytes or methaemoglobin when toxicity is suspected rather than as mandatory serial tests for every stable patient. Warn about fever/sore throat, jaundice, cyanosis, dyspnoea, rash with systemic illness, or unusual fatigue. ^[2]
• Follow symptoms, diet adherence, coeliac serology where useful, and previously abnormal tests. DXA is risk-stratified rather than automatic for every patient; routine repeat duodenal biopsy and routine lymphoma imaging are not indicated without clinical suspicion. ^[4]

Marker's trap listShowHide

Do not award a universal duodenal biopsy, universal baseline DXA, anti-gliadin testing, a routine 100–200 mg dapsone start, mandatory serial methaemoglobin, or a promised 6–12-month dapsone stop.

^{[2] [4]}

References4ShowHide

1. [1]Reunala T, Hervonen K, Salmi T. Dermatitis Herpetiformis: An Update on Diagnosis and Management Am J Clin Dermatol, 2021.PMID 33432477
2. [2]Nguyen CN, Kim SJ. Dermatitis Herpetiformis: An Update on Diagnosis, Disease Monitoring, and Management Medicina (Kaunas), 2021.PMID 34441049
3. [3]Görög A, Antiga E, Caproni M, et al. S2k guidelines (consensus statement) for diagnosis and therapy of dermatitis herpetiformis initiated by the European Academy of Dermatology and Venereology (EADV) J Eur Acad Dermatol Venereol, 2021.PMID 34004067
4. [4]Al-Toma A, Branchi F, Zingone F, et al. European Society for the Study of Coeliac Disease (ESsCD) 2025 Updated Guidelines on the Diagnosis and Management of Coeliac Disease in Adults. Part 2: Management, Follow-Up, and Complex Disease Courses United European Gastroenterol J, 2026.PMID 41831197