Dermatitis Herpetiformis

Related Subjects: |Colorectal cancer |Colorectal polyps |Ulcerative Colitis |Acute Severe Colitis |Crohn's disease |Coeliac disease |Dermatitis Herpetiformis

🍞🚫 A strict gluten-free diet is essential for managing dermatitis herpetiformis and represents the foundation of treatment, as it addresses both skin symptoms and any associated gastrointestinal manifestations.

ℹ️ About

• Dermatitis Herpetiformis (DH) 🩹 is an autoimmune blistering skin condition linked to gluten sensitivity and often associated with coeliac disease.
• Characterised by lifelong flare-ups and remissions 🔄, DH presents with intensely itchy skin lesions, often responsive to gluten withdrawal.
• While DH commonly occurs alongside coeliac disease, gastrointestinal symptoms may be subclinical or absent 🤐.

Prevalence and Risks

• 📊 Affects 0.4 to 3.5 per 100,000 people in the European population.
• 👨‍👩‍👧 Most commonly affects Caucasians, especially those aged 15-40 years, with a slightly higher prevalence in males.
• 🌍 Though more common in Caucasians, DH can occur across all age groups and ethnicities.

Aetiology and Pathophysiology

• Coeliac disease association 🍽️: DH is often seen in patients with coeliac disease, even if gastrointestinal symptoms are mild or absent.
• Subepidermal bullous disease 💥: DH is characterised by the deposition of IgA antibodies at the dermo-epidermal junction.
• The autoantigen 🎯 in DH is believed to be epidermal transglutaminase (TG3), distinct from the tissue transglutaminase (TG2) seen in coeliac disease.

Epidemiology

• 🌐 Incidence varies by region, with rates as low as 0.9 per 100,000 in Italy and up to 2.9 per 100,000 in Northern Ireland.

🩺 Clinical Features

• Skin symptoms 🤲: Intense itching and blistering vesicular rash primarily on extensor surfaces (e.g., elbows, knees, scalp, back, and buttocks).
• Lesion types 🔴: Includes small red spots, fluid-filled blisters, and wheals. Scratching worsens appearance and infection risk.
• Gastrointestinal involvement 🍽️: Gluten-sensitive enteropathy is common, though symptoms may be mild or absent.

Differential Diagnosis

• Eczema 🌿: DH may resemble eczema but differs in distribution and response to gluten withdrawal.
• Scabies 🕷️: Both cause intense itch, but scabies shows burrows and affects different areas.

🔎 Investigations

• Blood tests 💉: FBC, U&E, LFTs, folate for nutritional deficiencies.
• Serology 🧪:
  • Anti-endomysial IgA antibodies ✅: High sensitivity for coeliac disease.
  • Anti-tTG IgA antibodies 📈: Often elevated in DH and coeliac disease.
• Skin biopsy 🔬: Confirms DH with granular IgA at dermo-epidermal junction.
• Upper GI endoscopy (OGD) 📹: With duodenal biopsies to assess villous atrophy in coeliac disease.

💊 Management

• Gluten-free diet (GFD) 🍞🚫: Essential, lifelong, controls both skin and gut symptoms.
• Topical treatments 💊: Potent steroid creams may help itch during flares.
• Dapsone 💊:
  • First-line drug therapy; rapidly alleviates itch and lesions within days.
  • Side effects ⚠️: anaemia, neuropathy, methaemoglobinaemia → requires blood monitoring.
• Oral steroids 💉: Short-term option for severe flares unresponsive to other therapy.

⚠️ Complications

• Coeliac-related 🍽️: Malnutrition, anaemia, osteoporosis if untreated.
• Malignancy risk 🎗️: Increased risk of small bowel lymphoma and SCC.
• Skin infections 🦠: Secondary bacterial infection from scratching.

References

• Dermatitis Herpetiformis (Orphanet)

Cases

• Case 1 (Young adult): A 27-year-old man presents with a 1-year history of intensely itchy, blistering rash on his elbows, knees, and buttocks. He has scratched lesions to the point of excoriation. He denies GI symptoms, but bloods show iron-deficiency anaemia. Skin biopsy with direct immunofluorescence shows granular IgA deposition at the dermal papillae. Management: Gluten-free diet initiated, dapsone started for rapid symptom relief, and iron supplementation given. Outcome: Rash resolves within weeks on dapsone. At 6-month review, pruritus controlled with strict diet, dapsone tapered.
• Case 2 (Middle-aged woman): A 48-year-old woman presents with recurrent clusters of vesicles and papules on her scalp and extensor forearms, associated with severe nocturnal itch. She has a history of coeliac disease diagnosed 5 years earlier but has struggled with dietary adherence. Bloods show low folate. Skin biopsy again confirms IgA deposition. Management: Reinforced gluten-free dietary counselling, dapsone initiated at low dose, and folate replacement prescribed. Dermatology and dietitian co-manage care. Outcome: Significant improvement in rash within 4 weeks. Ongoing follow-up to monitor dapsone side effects (haemolysis, methaemoglobinaemia). Symptoms remain controlled with strict dietary compliance.

Teaching Commentary 🧑‍⚕️

Dermatitis herpetiformis is a chronic autoimmune blistering disorder, strongly associated with coeliac disease. It arises from IgA deposition in dermal papillae, leading to intensely pruritic vesicles on extensor surfaces. Many patients have subclinical intestinal changes even without GI symptoms. Diagnosis is by skin biopsy with immunofluorescence. Management is strict gluten-free diet (which treats both DH and coeliac enteropathy) and dapsone for rapid cutaneous relief. Monitoring is essential for drug side effects and nutritional deficiencies. Prognosis is good with adherence to therapy, but non-compliance increases risk of lymphoma.