Makindo Medical Notes

Related Subjects: |Nikolsky's sign |Koebner phenomenon |Erythema Multiforme |Pyoderma gangrenosum |Erythema Nodosum |Dermatitis Herpetiformis |Lichen Planus |Acanthosis Nigricans |Acne Rosacea |Acne Vulgaris |Alopecia |Vitiligo |Urticaria |Basal Cell Carcinoma |Malignant Melanoma |Squamous Cell Carcinoma |Mycosis Fungoides (Sezary Syndrome) |Xeroderma pigmentosum |Bullous Pemphigoid |Pemphigus Vulgaris |Seborrheic Dermatitis |Pityriasis/Tinea versicolor infections |Pityriasis rosea |Scabies |Dermatomyositis |Toxic Epidermal Necrolysis |Stevens-Johnson Syndrome |Atopic Eczema/Atopic Dermatitis |Psoriasis

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.

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 Presentation

• 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 often worsens the appearance and increases infection risk.
• Gastrointestinal involvement: While gluten-sensitive enteropathy is common, symptoms may be mild or absent. Patients may experience weight loss, diarrhoea, constipation, bloating, and abdominal discomfort in severe cases.

Differential Diagnosis

• Eczema: DH may resemble eczema but differs in its distribution and response to gluten withdrawal.
• Scabies: Both conditions present with intense itching; however, scabies typically affects different areas and shows burrows on the skin.

Investigations

• Blood tests: FBC, U&E, LFTs, and folate levels to assess nutritional deficiencies commonly seen in associated coeliac disease.
• Serology:
  • Anti-endomysial IgA antibodies: High sensitivity for coeliac disease.
  • Anti-tTG IgA antibodies: Often elevated in both DH and coeliac disease but may vary depending on the gluten intake.
• Skin biopsy: Performed by a dermatologist, it is crucial for confirming DH, showing granular IgA deposits at the dermo-epidermal junction on immunofluorescence.
• Upper GI endoscopy (OGD): Recommended with duodenal biopsies to confirm changes associated with coeliac disease, such as villous atrophy.

Management

• Gluten-free diet (GFD): Essential and lifelong to control skin and intestinal symptoms, and reduces the need for medications. Many patients see an improvement in skin symptoms within months of strict adherence.
• Topical treatments: Strong steroid creams may provide relief from itching during flare-ups or while awaiting biopsy results.
• Dapsone:
  • First-line pharmacological treatment for DH; rapidly alleviates itching and lesion formation within days.
  • Side effects include anaemia, neuropathy, and methemoglobinemia, necessitating regular monitoring of blood counts and haemoglobin levels.
• Oral steroids: Occasionally used for severe flare-ups unresponsive to other treatments but are typically reserved for short-term use.

Complications

• Risk of coeliac-related complications: Untreated DH can lead to coeliac disease complications, such as malnutrition, osteoporosis, and anaemia due to chronic malabsorption.
• Increased malignancy risk: Similar to coeliac disease, DH is associated with an increased risk of certain cancers, including small bowel lymphoma and squamous cell carcinoma.
• Skin infections: Secondary bacterial infections may occur due to scratching.

References

• Dermatitis Herpetiformis