Dermatitis Herpetiformis

Autoimmune bullous disorder associated with coeliac disease

Aetiology

  • Strong association with coeliac disease
    • 90% DH patients have gluten sensitive enteropathy (may be asymptomatic)
  • Associated with HLA-DQ2 haplotype
  • Peak incidence 15-40 years

Pathophysiology

  • IgA antibodies target gliadin component of gluten but cross react with connective tissue matrix proteins (tissue transglutaminase - TTG)
  • Immune complexes form in dermal papillae and activate complement and generate neutrophil chemotaxins → inflammation → subepidermal blisters

Clinical presentation

  • Intensely itchy symmetrical lesions on an erythematous and swollen base
    • Itch can precede blisters
  • Elbows, knees and buttocks often excoriated

Investigations

Bloods

  • Anti-TTG

Biopsy

  • Immunoflorescence - will show granular deposits of IgA in dermal papillae
  • Histology - sub-epidermal blisters with papillary micro-abscesses

Management

  • Gluten free diet +/- dapsone

Complications

  • Rare but significantly increased risk of small bowel lymphoma