Epidermolysis Bullosa (EB) is a group of genetic skin conditions that cause the skin to blister and tear at the slightest touch. Those born with EB have skin so fragile that they are often called ‘butterfly children’ – as their skin is quite simply as fragile as the wing of a butterfly. Painful open wounds and sores form where the skin is damaged, and in some cases, internal linings and organs are also affected. Complications as a result of secondary infection and extensive scarring are factors that people living with EB often have to face. Tragically, certain types of EB can be fatal in infancy and others are severely life-limiting. EB may be inherited in either a dominant or recessive form. In dominant EB, one parent usually carries the gene and is affected by the condition themselves, while the birth of a child suffering from the recessive form is usually completely unexpected since both parents can carry the EB gene without displaying the condition themselves. In dominant EB, there is a 50% chance of passing the disorder to children, whilst in recessive EB the chance is 25%. EB can also arise through a new spontaneous mutation, where neither parent carries EB but the gene mutates spontaneously in either the sperm or the egg before conception. Rarely, a severe form of EB can be “acquired” as the result of autoimmune disease, where the body develops antibodies to attack its own tissue proteins.
There are three main types of EB:
1- EB Simplex
The most common form of Epidermolysis Bullosa, EB Simplex (EBS) is characterized by a lack of adhesion of the skin directly above the basement membrane (the basal layer).
Most forms of EBS are inherited as dominant traits meaning the parents also demonstrate visible clinical signs of the condition. EBS typically manifests itself as blistering confined to the hands and feet. In another form of EBS, skin blisters can occur all over the body.
Blistering generally appears during the neonatal period but it can also manifest itself in later childhood (or even in adult life). Painful skin blisters can occur by rubbing, especially on the feet where footwear causes increased irritation. People living with EBS have to cope with a range of complications, rubbing is worse in warm weather and infections are common.
2- Dystrophic EB
Dystrophic EB (DEB) is a genetic skin condition characterized by a lack of adhesion of the skin under the basement membrane. DEB may be inherited as a dominant or recessive trait. DEB derives its name from the tendency of the blisters to heal with scarring, leading to contraction of the joints, fusion of the fingers and toes, contraction of the mouth membranes and narrowing of the oesophagus.
The severity of DEB varies widely. Often the dominant inherited type of DEB is the least severe type and the patient can lead an almost normal life. However, the severity of the condition can increase with age due to scarring, the fusion of the fingers and wastage of skin tissue.
People living with Recessive DEB (RDEB) have a high chance of developing a squamous cell carcinoma (a form of aggressive skin cancer) before the age of 35.
3- Junctional EB
Junctional EB (JEB) is characterized by a lack of adhesion of the skin through the basement membrane. JEB is inherited recessively which means that the parents are both carriers, often unknowingly, and do not show physical signs of the skin condition. The birth of a child with JEB is therefore totally unexpected.
JEB generalized severe (previously Herlitz JEB), which affects around half of those diagnosed with JEB, is usually fatal in infancy with only a few babies surviving to the second or third year of life. These infants usually die from malnutrition and anemia due to serious blistering in the pharynx and the oesophagus.
The milder form of JEB, JEB generalized intermediate (previously Non-Herlitz JEB), does not impose life restrictions but can cause life-long pain and disability.
The confirmation and diagnosis of EB (sub) types depends on laboratory diagnosis in newborn infant or people with mild to severe symptoms. The inheritance pattern (a parent passing a gene on to their child) is only possible with genetic testing in the families. EB is generally classified in to four main types depending upon the foci of splitting the skin layers.
In Epidermolysis Bullosa simplex (EBS), Splitting occurs in the most superficial layer of the skin (upper layer) Junctional Epidermolysis Bullosa- Splitting occurs between the structures that keep the most superficial layer (epidermis) and the deep layer (dermis) together, known as basement membrane. Dystrophic Epidermolysis bullosa – splitting occurs below the membrane within the superficial dermis and in KS, blistering can occur at multiple and different levels within the skin.
They are more than 20 Disease causing (pathogenic) variants associated with Epidermolysis Bullosa (EB). These genes encode structural and functional proteins laminins and integrins, after translation that provide skin integrity and resistance.