Dermatitis herpetiformis - Bullous disorders

Dermatitis herpetiformis

Definition

Dermatitis herpetiformis is a primary blistering disorder associated with coeliac disease and other autoimmune disorders.

Prevalence

1 in 350–400 patients with coeliac disease.

Age

Teenagers and young adults.

Sex

M > F

Aetiology

Eighty-five per cent of individuals with dermatitis her-petiformis have small bowel mucosal changes with variable villous atrophy on small bowel biopsy even if they do not have the clinical features of coeliac disease. Both disorders have similar HLA haplotypes and autoantibodies to endomysial, gliadin and reticulin antigens. Dermatitis herpetiformis is also associated with other organ specific autoimmune conditions.

Clinical features

Erythematous itchy papules and vesicles over the extensor surface of the extremities and on the trunk.

Investigations

It is a clinical diagnosis; however, biopsy of affected skin shows a subepidermal blister with neutrophil infiltration. Immunofluorescence staining of skin biopsy taken from an unaffected area shows granular IgA deposits along the basement membrane. Serological testing and small bowel biopsy may be required to identify gluten sensitivity.

Management

Even without clinical coeliac disease patients often respond to a gluten-free diet. The rash responds dramatically to dapsone (this has been used as a diagnostic test). The concomitant use of cimetidine (which inhibits cytochrome p450 enzymes) helps to reduce side effects caused by the metabolic products of dapsone.

Prognosis

Condition often shows relapses and remissions.