Dermatitis herpetiformis

Published on 02/04/2015 by admin

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178 Dermatitis herpetiformis

Instruction

Look at this patient’s skin, who in the past had chronic diarrhoea.

Salient features

History

• History of diarrhoea

• History of gluten intolerance (although these patients rarely have gross malabsorption)

• Ask the patient whether the rash itches.

Examination

• Dry, itchy vesicles and urticarial plaques (Fig. 178.1) occurring bilaterally and symmetrically over the extensor surfaces, elbows, knees, posterior neck, back and buttocks.

Fig. 178.1 Dermatitis herpetiformis. (A) Pruritic, urticarial papules and small blisters. (B) Occurrence in the lumbosacral area.

(With permission from Habif 2009.)

Proceed as follows:

• Look for similar lesions on the scalp, face, neck, shoulders, buttocks, knees and calves.

Diagnosis

This patient has itchy vesicles on the elbows (lesion) caused by dermatitis herpetiformis (functional status).

Advanced-level questions

From which other itchy skin disorder should dermatitis herpetiformis be differentiated?

What are the extracutaenous manifestations of dermatitis herpetiformis?

• Gluten-sensitive enteropathy (frequent, asymptomatic)

• Thyroid dysfunction (especially hypothyroidism)

• Lymphoma (especially GI).

How would you investigate such a patient?

• Skin biopsy: fibrin and neutrophils accumulate selectively at the tips of dermal papillae, forming small microabscesses. Subepidermal vesicles have a neutrophilic infiltrate. Immunofluorescence demonstrates granular dermal papillary immunoglobulin A deposits

• Circulating anti-endomysium antibodies are present in all cases

• Jejunal biopsy: patchy abnormality showing subtotal villous atrophy with increased lymphocyte infiltration in the epithelium

• Therapeutic test: dapsone dramatically reduces itching in 72 h, often providing confirmation before the biopsy result is available

• HLA-B8 and HLA-DRw3 are positive in >80% of patients.

How would you treat such a patient?

• Gluten restriction (Br J Dermatol 1994;131:541)

• Dapsone or sulfapyridine: neither drug should be given to a patient with glucose-6-phosphate dehydrogenase deficiency. Treatment is lifelong; there is usually a rapid relapse if the drug is stopped.

In which foods is gluten found?

Wheat, barely and rye (rice and maize are permitted in these patients).

Is it advisable for these patients to add oats to their gluten-free diets?

Moderate amounts of oats can be ingested without harmful effects in coeliac disease (N Engl J Med 1995;333:1033–7, BMJ 1996;313:1300–1) and in dermatitis herpetiformis (N Engl J Med 1997;337:1884–7, Gut 1998;43:490–3). Oats do not contain gliadin but do have avenin. However, as avenin makes up only 5–15% of the total protein content, even if it were as toxic as gliadin (a fact that is not universally conceded), a large amount of oats would need to be ingested to bring about an equivalent effect, in terms of the amount of protein ingested.

What do you know about gluten?

Gluten is the protein component that persists following the removal of water and starch from defatted flour. Gliadin is a class of protein found in the gluten fraction of flour. There are four gliadin fractions (α, β, γ and ω). α-Gliadin is injurious to the small intestinal mucosa, although there is some disagreement about the toxicity of other peptides. Patients with dermatitis herpetiformis develop IgA and IgG antibodies to gliadin and reticulin (the latter a component of the anchoring fibrils that tether the epidermal basement membrane to the upper dermis).

What are the benefits of a gluten-free diet?

It gradually improves skin lesions, improves any associated manifestations of malabsorptive enteropathy and may reduce the late risk of intestinal lymphoma. It also normalizes histological abnormalities.

Note: An elemental diet lacking protein has been reported to benefit patients with dermatitis herpetiformis even in the presence of a gluten challenge.

Dermatitis herpetiformis was first described in 1884 by LA Duhring (1845–1913), Professor of Diseases of the Skin at the University of Pennsylvania. He studied dermatology in Paris, London and Vienna, and wrote the first American textbook of dermatology. Others believe that dermatitis herpetiformis was first described by F von Hebra, who also wrote a textbook of dermatology.

Samuel J Gee (1839–1911) of St Bartholomew’s Hospital, London, provided the first thorough description of coeliac sprue in 1888 (Gee S On the coeliac affection. St Barth Hosp Rep 1888;24:17–20).

Dutch paediatrician WK Dicke astutely observed that wheat and rye were harmful in children with this disease (Dicke WK Coeliac disease: investigation of the harmful effects of certain types of cereal on patients with coeliac disease. Doctoral thesis, University of Utrecht, The Netherlands, 1950; N Engl J Med 1995;333:1075–6).

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