Bullous skin diseases: pemphigus and pemphigoid explained

What these conditions are

The skin is held together like a wall, with cells stuck to one another and anchored to the layers beneath. In bullous diseases, the immune system, which normally defends the body, makes a mistake and attacks the 'glue' that holds skin cells together. This weakens the join, so fluid collects and blisters form. Pemphigus and pemphigoid are both autoimmune blistering conditions, but they attack different levels: in pemphigus the split is higher up, within the outer skin layer, so the blisters are fragile; in pemphigoid the split is deeper, so the blisters are tense and tougher. Neither is caught from someone else, and neither is caused by poor hygiene. They are uncommon, tend to affect adults, and pemphigoid in particular is more common in older people.

Pemphigus: what to look for

In pemphigus, because the skin splits within its outer layer, the blisters are thin-walled and fragile, so they often break easily to leave raw, sore areas rather than intact bubbles. A very characteristic feature is that the mouth is frequently affected, and painful mouth ulcers and sores can be the first sign, sometimes appearing before any skin blisters and making eating uncomfortable. The skin blisters and raw areas can occur on many parts of the body. Because the raw areas can be widespread and lose fluid, and can become infected, pemphigus can make people quite unwell and needs prompt specialist treatment. Anyone with unexplained, persistent mouth ulcers together with fragile skin blisters or raw patches should be assessed by a doctor, as recognising the pattern early helps get the right care started.

Pemphigoid: what to look for

In pemphigoid, the split is deeper in the skin, so the blisters are tense, firm and filled with fluid, and they tend not to burst as easily as in pemphigus. They often appear on the arms, legs, tummy and in skin folds, and are frequently very itchy; sometimes there is itching and red, raised patches for a while before the blisters develop. The mouth is affected less often than in pemphigus. Pemphigoid is more common in older adults. Although the tense blisters look dramatic, the condition can often be brought under good control with treatment. As with pemphigus, the raw areas left when blisters do break need care to prevent infection. Any new, persistent blistering rash, particularly a very itchy one in an older adult, should be checked by a doctor rather than assumed to be a simple reaction.

How they are diagnosed

Because several conditions can cause blisters, doctors confirm bullous diseases with specific tests rather than by looking alone. Usually a dermatologist takes a small sample of skin, called a biopsy, from in and around a blister. This is examined under a microscope and with special techniques that can show the tell-tale pattern of antibodies attacking the skin, revealing exactly which layer is affected and helping distinguish pemphigus from pemphigoid and from other blistering conditions. Blood tests can also detect the antibodies involved and help monitor the condition over time. Reaching a precise diagnosis matters because the different conditions are managed slightly differently and need specialist input. If your GP suspects a bullous disease, they will usually refer you to a dermatology service, where these tests can be arranged.

Treatment and living with them

Treatment for pemphigus and pemphigoid is led by a dermatology specialist and aims to calm the overactive immune attack and let the skin heal, then to keep the condition under control with as little medicine as possible over time. Because the treatments quieten the immune system, people are usually monitored carefully for side effects and for infections, and looking after the skin, keeping raw areas clean and treating any infection promptly are all important. Good mouth care helps when the mouth is involved. These are long-term conditions that often need ongoing treatment and follow-up, but with modern care most people can achieve good control and get on with life. Keeping in touch with the specialist team, attending reviews, and seeking advice early if the blistering flares or areas become infected all help keep things on track.