Overview

Dermatitis herpetiformis

Investigations

Coeliac disease is caused by sensitivity to the protein gluten. Repeated exposure leads to villous atrophy which in turn causes malabsorption. Conditions associated with coeliac disease include dermatitis herpetiformis (a vesicular, pruritic skin eruption) and autoimmune disorders (type 1 diabetes mellitus and autoimmune hepatitis).

Diagnosis is made by a combination of serology and endoscopic intestinal biopsy. Villous atrophy and immunology normally reverses on a gluten-free diet.

NICE issued guidelines on the investigation of coeliac disease in 2009. If patients are already taking a gluten-free diet they should be asked, if possible, to reintroduce gluten for at least 6 weeks prior to testing.

Serology

• tissue transglutaminase (TTG) antibodies (IgA) are first-choice according to NICE
• endomyseal antibody (IgA)
  • needed to look for selective IgA deficiency, which would give a false negative coeliac result
  • if IgA deficiency test for IgG endomyseal antibodies, IgG deamidated gliadin peptide (DGP) or IgG transglutaminase antibodies
• anti-gliadin antibody (IgA or IgG) tests are not recommended by NICE
• anti-casein antibodies are also found in some patients

Endoscopic intestinal biopsy

• the 'gold standard' for diagnosis - this should be performed in all patients with suspected coeliac disease to confirm or exclude the diagnosis
• traditionally done in the duodenum but jejunal biopsies are also sometimes performed
• findings supportive of coeliac disease:
  • villous atrophy
  • crypt hyperplasia
  • increase in intraepithelial lymphocytes
  • lamina propria infiltration with lymphocytes

Rectal gluten challenge has been described but is not widely used

Duodenal biopsy from a patient with coeliac disease. Complete atrophy of the villi with flat mucosa and marked crypt hyperplasia. Intraepithelial lymphocytosis. Dense mixed inflammatory infiltrate in the lamina propria. © Image used on license from PathoPic

Duodenal biopsy from a patient with coeliac disease. Flat mucosa with hyperplastic crypts and dense cellular infiltrate in the lamina propria. Increased number of intraepithelial lymphocytes and vacuolated superficial epithelial cell vacuolated superficial epithelial cells. Higher magnification image on the right. © Image used on license from PathoPic