Investigations

The investigation of dermatitis herpetiformis should include the following:

• blood tests for celiac disease
  • immunology study
  • IgA antiendomysial antibodies
  • IgA anti-tissue transglutaminase antibodies (sensitivity 98.5%, specificity 98%)
  • useful additional test if serology supports the diagnosis of coeliac disease include
    • FBC
    • blood film
    • haematinics (vitamin B12, folate, ferritin)
    • urea and electrolytes may
    • thyroid function test – due to the association of thyroid disease with both coeliac disease and dermatitis herpetiformis
  • skin biopsies
    • lesional skin of patients with DH will reveal epidermal vesicles and blisters associated with accumulation of neutrophils at the papillary tips on histopathological study
    • a second biopsy consisting of peri-lesional skin (within 2cm of the blister) is used for direct immunofluorescence
      • is the gold standard for the diagnosis of DH
      • will show granular IgA deposits along the dermal-epidermal junction and on top of the dermal papillae

If blood tests point towards a diagnosis of celiac disease, a referral to secondary care is recommended.

Note:

• once the diagnosis is confirmed, DH should be considered as a cutaneous manifestation of and pathognomonic for, coeliac disease. Hence, duodenal or jejunal biopsies are not considered necessary for further diagnosis

Reference:

• (1) Jakes AD, Bradley S, Donlevy L.Dermatitis herpetiformis. BMJ. 2014;348:g2557.
• (2) Antiga E, Caproni M.The diagnosis and treatment of dermatitis herpetiformis. Clin Cosmet Investig Dermatol. 2015;8:257-65.
• (3) Primary Care Dermatology Society (PCDS). Dermatitis herpetiformis (Accessed 20/03/2017)