Epidermolysis Bullosa

Epidermolysis bullosa (EB) is caused by an inherited genetic mutation that makes skin more fragile.

A genetic mutation occurs wheninstructions carried in certain genes become 'scrambled'. This results in some of the body's processes not working in the normal way.

How EB is inherited

All genes in your body come in pairs. You receive one half from your mother and the other half from your father.

Genetic conditions such as EB and the mutations which causethemcan be passed down through families in two ways:

• it takesonlyone mutated gene for you to develop the symptoms of a particular genetic condition. The parentyou inherited the mutated gene from will also have symptoms of the condition this is known as autosomal dominant inheritance
• both genes in the pair need to have the same mutation before you develop symptoms of the condition. You would need to inherit one mutated gene from your mother and another from your father. In this case, neither parent would have any symptoms of the condition as they would only be a carrier of the mutated gene this is known as autosomal recessive inheritance .

In EB, some variants are autosomal dominant and others are autosomal recessive.

Epidermolysis bullosa simplex

Epidermolysis bullosa simplex (EBS) is an autosomal dominant condition. If you have EBS, one of your parents also has a history of the condition and has passed the mutated gene to you. However, if their symptoms are mild, their condition may not have been diagnosed.

You may be the first in your family to be affected. In these cases, the mutation will have occurred in the womb before you were born. Neither of your parents carries the mutation and you havea new mutation.

If you go on to have children, they'll have a 50% chance of developing EBS.

Junctional epidermolysis bullosa

Junctional epidermolysis bullosa (JEB) is an autosomal recessive condition. If you have JEB, both your parents are carriers of the mutated gene but they don't have symptoms.

Your children are only at risk of developing JEB if your partner is also a carrier of a mutated gene known to be associated with JEB. It's difficult to estimate exactly how many people are carriers of the various JEB mutated genes, butthe number is thought to be low.

If you and your partner are both carriers of a JEB mutated gene, your children have aone-in-four chance of developing the condition.

Dystrophic epidermolysis bullosa

Depending on the particular variant, dystrophic epidermolysis bullosa can be either autosomal recessive or dominant.

Dominant DEB is autosomal dominant and the other types are autosomal recessive.

Skin layers

Human skin is made of three layers:

• epidermis the outer layer of skin
• dermis the middle layer of skin
• subcutis the deepest layer of skin, mainly made up of fat

The epidermis and dermis meet at a point known as the basement membrane zone (BMZ). This contains specialised proteins that keep the two layers stuck securely together.

Faulty genescan causeone or more proteins in the BMZ to not work properly. This meanstrauma or friction to an area of skin could result in the epidermis and dermis becoming unstuck. If the two layers become separated, a space is created which fills with fluid to form a Blisters .