Synopsis
Recognise intensely itchy excoriated extensor disease as a cutaneous expression of gluten-sensitive enteropathy, confirm granular IgA correctly, and combine a strict gluten-free diet with safe dapsone treatment.
- Dermatitis herpetiformis is a very itchy symmetrical eruption of grouped papules and small vesicles on elbows, knees, buttocks, shoulders and scalp; scratching often removes intact blisters before examination.
- The name describes a herpes-like grouping, not herpes infection. It is the skin manifestation of gluten-sensitive coeliac disease and can occur without gastrointestinal symptoms.
- Take direct-immunofluorescence tissue from normal-appearing perilesional skin, not an excoriated lesion; granular IgA at dermal papillary tips is the diagnostic pattern.
- Check total IgA with IgA tissue transglutaminase while the person is still eating gluten and use an IgG-based pathway when IgA deficient.
- A strict lifelong gluten-free diet treats intestinal disease, nutritional and lymphoma risk and eventually reduces the skin's dapsone requirement, but improvement takes months to years.
- Dapsone controls itch and new lesions within days but does not heal gluten-sensitive enteropathy; it is a bridge and adjunct, not a substitute for dietetic treatment.
- Before dapsone, check G6PD, full blood count, reticulocytes, liver and renal function and establish frequent early blood monitoring.
- Dapsone commonly lowers haemoglobin and raises methaemoglobin to some degree; clinically important cyanosis, dyspnoea, jaundice, fever or mouth ulcers requires urgent testing and cessation.
- Do not advise gluten withdrawal before coeliac serology, histology or specialist diagnosis unless unavoidable, because reduced exposure lowers diagnostic sensitivity.
Key red flags
Rapidly blistering or painful skin, extensive mucosal disease, fever, weight loss, persistent diarrhoea, severe anaemia, neurological symptoms or dapsone toxicity is not routine dermatitis herpetiformis follow-up and needs urgent assessment.
Cyanosis, dyspnoea, jaundice, dark urine, fever, mouth ulcers, bruising or widespread rash while taking dapsone requires urgent cessation and investigation.
Investigation priorities
Detect the characteristic IgA deposits while avoiding excoriated, inflamed tissue that has lost them.
Management branches
A symmetrical excoriated extensor eruption raises dermatitis herpetiformis.
- Document distribution, intact vesicles, treatment, diet, bowel and deficiency symptoms and photograph a fresh representative area with consent.
- While gluten is still being eaten, take normal perilesional skin for direct immunofluorescence and a separate lesion for routine histology when useful, then request total IgA and IgA tTG.
- Refer confirmed or strongly suspected disease to dermatology and gastroenterology for integrated skin, coeliac and nutritional assessment before recommending lifelong restriction.