Bullous pemphigoid is a blistering skin disease that tends to affect the elderly.
It's caused by a problem with the immune system, but usually goes away on its own within a few years. In the meantime, blisters can be controlled with medication.
About one in 10,000 people are affected by bullous pemphigoid each year in the UK.
What are the symptoms?
Bullous pemphigoid typically starts with a red, itchy rash that looks a bit like eczema or hives. This tends to last several weeks or months.
Then, groups of large, itchy blisters usually appear on the red patches, just beneath the surface of the skin. They can be up to 5cm in diameter and full of fluid, with the thick skin of the blisters stretched tightly.
The fluid inside is usually clear, but can turn cloudy or blood stained.
Blisters last a few days before healing without leaving a scar, but a cycle develops in which more form.
The rash and blisters are usually seen on the upper arms and thighs, sometimes spreading to body folds and the abdomen (tummy).
However, some people have no symptoms, or just have mild redness and irritation.
Who is affected?
The condition is usually seen in older people aged over 70. Rarely, it can affect children and younger adults.
Both men and women are affected equally.
What is the cause?
Bullous pemphigoid is an autoimmune condition, which means the immune system attacks the body's own tissues and organs.
In bullous pemphigoid, the person's immune system produces antibodies against the skin. These antibodies attack the basement membrane, which lies between the skin's top layer (epidermis) and next layer (dermis) and holds the skin together. The skin layers start to separate and fluid builds up in between.
It's not understood why autoimmune diseases like bullous pemphigoid happen, but it's thought that something triggers the immune system to attack the body's own tissues. Certain medicines and sunburn have been known to act as a trigger.
Symptoms usually come on unexpectedly.
Bullous pemphigoid is not:
caused by an allergy
affected by diet or lifestyle
How is it diagnosed?
Your GP may suspect bullous pemphigoid just by looking at your skin.
The diagnosis is then confirmed by taking a small sample of your affected skin (biopsy) and sending it to a laboratory to be inspected, to see if the top layers of skin have separated.
Special staining (immunofluorescence) may be used to show up the antibodies, and a blood sample may be taken and checked for the presence of pemphigoid antibodies.
How is it treated?
If you have been diagnosed with bullous pemphigoid you'll probably be referred to a dermatologist (skin specialist) for treatment.
The aim of treatment is to stop new blisters forming and to heal the blisters that are already there.
Your specialist may prescribe quite powerful medication with potentially severe side effects, so the smallest possible dose is used to minimise these side effects.
You'll usually be prescribed corticosteroids (either tablets or cream), sometimes alongside 'steroid-sparing' medication that allows doctors to reduce the dose of steroids. You may also be prescribed an antibiotic.
Corticosteroids, or steroids, are an anti-inflammatory medicine prescribed for a wide range of conditions.
If the affected area of skin is only small, you may be prescribed steroid cream to rub into the area.
If the blisters are severe, you may be given a high dose to start with, to get the condition under control and to stop the blisters appearing. This may take several weeks. Then, the dose is gradually reduced, and you'll either come off the steroids or be kept on a low dose for a long time.
To use the lowest possible effective dose of steroids, your doctor may give you 'steroid sparing' medicine to take alongside, which is described below.
Tablets to suppress your immune system
You may be prescribed azathioprine or methotrexate medicine to take alongside steroids. These work by suppressing your production of antibodies.
The idea is that side effects will be less troublesome if low doses of two different tablets (steroids and immunosuppressants) are used instead of one high dose of steroids. This is known as 'steroid sparing'.
Looking after your skin
Blisters should be left intact, if possible, to reduce your risk of infection.
However, if they're particularly large and in a difficult place – like on the sole of your foot – they may be carefully pierced with a sterile needle to release the fluid. The skin of the blister should be left.
If blisters do break, they heal quickly.
It's not possible to cure the condition with treatment, but it usually goes away on its own within five to six years.
In the meantime, medication is effective in keeping the blisters under control.