Dermatitis herpetiformis

What is dermatitis herpetiformis?

Dermatitis herpetiformis (also known as Duhring's disease) is a rare, very itchy and persistent breakout of blisters.

What causes dermatitis herpetiformis?

Dermatitis herpetiformis is associated with a bowel condition known as celiac disease (disease of the small intestine). Virtually all patients with dermatitis herpetiformis probably have subtle variations of this condition. In some it will be clinically apparent, but in most it will be so mild that it causes no symptoms and generally does not require any complicated investigation. In both conditions the patients are sensitive to gluten, a protein found in wheat and rye flour. An immunological reaction to gluten plays an important part in causing the rash of dermatitis herpetiformis.

Is dermatitis herpetiformis hereditary?

One out of 10 patients with this condition has a family history of either dermatitis herpetiformis or of celiac disease.

What are the symptoms of dermatitis herpetiformis?

• Intense itching is the first main symptom.
• Symptoms of an associated celiac disease may be present in a minority of patients with dermatitis herpetiformis, but are usually mild. This includes weight loss, abdominal discomfort and pale-coloured bowel motions.

What does dermatitis herpetiformis look like?

Dermatitis herpetiformis usually first appears in young and middle-aged adults but is occasionally seen in children. The rash consists of small red spots, small tense fluid-filled blisters and wheals. The most common body parts that are usually affected are the elbows, knees, scalp, bottom and back. If left untreated, dermatitis herpetiformis usually runs a very long course, often over many years. Sometimes it improves or worsens, but it may eventually disappear completely.

How is dermatitis herpetiformis diagnosed?

The rash may be difficult to diagnose, as it is often confused with much more common skin conditions such as scabies and eczema. A skin biopsy taken by a dermatologist is usually needed to confirm the diagnosis. It is important to do this test as treatment may involve long-term use of medication or a change in diet. The biopsy usually involves two separate laboratory tests. Blood tests are usually performed as well. A small specimen may also be taken from the inner lining of the bowel to check for the type of inflammation that is seen in celiac disease.

Can dermatitis herpetiformis be cured?

No. All traces of dermatitis herpetiformis may disappear with treatment, but they will recur when the treatment is stopped.

How can dermatitis herpetiformis be treated?

Diet

Most doctors recommend that all patients with dermatitis herpetiformis should be on a gluten-free diet. This is complicated to maintain and your dermatologist will involve specialist dieticians. The diet is slow to work but should:

• decrease and eventually remove the need to take medication
• reduce any bowel symptoms
• cut the risk of getting a bowel lymphoma - a complication that may rarely occur if celiac disease remains untreated for years.

Medication

Dermatitis herpetiformis may also be treated with an anti-infective drug called dapsone. However, this may have side effects, so treatment does not usually start until laboratory tests have confirmed the diagnosis. Dapsone slightly decreases the patient's red cell count and haemoglobin (the oxygen-carrying part of the red cells) levels. This is usually dosage-related and monitored with blood tests. However, a few patients may experience a rapid drop in their blood counts. For this reason, blood tests are performed weekly at first, and patients are asked to urgently report any unusual symptoms (sore throat, dizziness or faintness) to their doctor. Dapsone also causes some patients to have headaches.

What can I do?

Remember that you need to strictly adhere to your diet for a long time. About 80% of patients with dermatitis herpetiformis do well with a gluten-free diet; but it may take as long as a year before they are able to reduce their dapsone dosage. After that, some of them will be able to stop taking dapsone completely.

References

1. DERMATITIS HERPETIFORMIS ONLINE COMMUNITY, THE. www.dermatitisherpetiformis.org.uk/
2. DERMNET NZ. Website: www.dermnetnz.org/dna.dh/dh.html
3. MILLER, JL MD. 14 August 2009. Dermatitis herpetiformis.
Website: www.emedicine.com/DERM/topic95.htm