Dermatitis herpetiformis

Dermatitis herpetiformis (DH) is an autoimmune skin condition linked to coeliac disease.

DH affects around 1 in 3,300 people. This is fewer people than coeliac disease.

DH can appear at any age, but is most commonly diagnosed between the ages of 15 and 40.

It's more common in men than women, and is rare in children.

Symptoms

People with DH can have:

  • red, raised patches, often with blisters that burst with scratching
  • severe itching and often stinging

The rash can affect any area of the skin but is most commonly seen on the:

  • elbows
  • knees
  • buttocks

The rash usually occurs on both sides of the body.

Gut symptoms

Most people with DH have the same kind of gut damage seen with coeliac disease, but may not complain of gut symptoms like:

  • diarrhoea
  • constipation
  • stomach pain
  • bloating

Just over half (60%) of people with DH don't have gut symptoms.

Causes

DH is caused by the body's immune system reacting to a protein called gluten. Gluten is found in foods containing wheat, barley and rye.

This reaction causes a skin rash to develop.

Diagnosis

A diagnosis of DH is confirmed by a skin test called a skin biopsy. A skin biopsy is a procedure where a sample of skin is removed to be tested.

What's involved in a skin biopsy?

During this test, a specialist skin doctor called a dermatologist will take a small sample of skin from an area without the rash. Samples of skin taken from the area with the rash don't always give an accurate result.

The skin sample is then tested. If you test positive for DH, you'll be referred to a specialist gut doctor called a gastroenterologist to be tested for coeliac disease.

Diet before and during diagnosis

To ensure an accurate skin test is taken first time, it's important that you keep eating gluten-containing foods before and during diagnosis.

If you have already removed gluten from your diet, you must reintroduce it in more than 1 meal every day for at least 6 weeks before having the tests.

Treatment

The treatment for DH is a lifelong gluten-free diet.

The length of time it takes for the skin to heal varies from person to person, but it can take up to 2 years or more.

Gluten-free diet

A gluten-free diet is when all gluten-containing foods are removed from your diet.

Gluten is found in wheat, barley and rye and sometimes people are sensitive to oats too.

A gluten-free diet should only start once a confirmed diagnosis of DH is given.

Medication during treatment

Some patients will be given medication to help them over this period of recovery.

Medication will only be given to control the skin itching and blisters. It won't treat any other symptoms.

The drug most likely to be used is called Dapsone.

Dapsone

Dapsone is taken in tablet form and must be swallowed.

It helps ease the itching and controls the development of blisters. It should work within a few days.

If you stop taking Dapsone before the gluten-free diet has taken effect, the rash will return.

Side effects of Dapsone

The most common side effect of Dapsone is anaemia (a deficiency of red cells or haemoglobin in the blood).

Less common side effects are headaches and depression. Nerve damage is rare.

Because of these side effects, you'll always be prescribed the lowest effective dose. Your DH should be monitored once the drug dose has been reduced.

Alternatives to Dapsone

Some people can't tolerate Dapsone. If you're one of these people, the following drugs can also be taken to clear the rash:

  • Sulphapyridine
  • Sulphamethoxypyridazine

Complications

The same associated conditions and complications can occur in people with DH as in people with coeliac disease.

Some potential complications of DH include:

  • osteoporosis
  • certain kinds of gut cancer
  • an increased risk of other autoimmune diseases – such as type 1 diabetes and thyroid disease.

As with coeliac disease, the risk of developing these is reduced by following a gluten-free diet.

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