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 features

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

• Also other features of coeliac disease e.g. diarrhoea, abdominal pain, fatigue

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