Epidermolysis bullosa (EB) is a genetic skin disorder characterized by skin tearing and blistering at the slightest touch. It usually occurs at birth, but sometimes the symptoms are mild and detected only when the child is older.
There also is a non-genetic type of EB, called epidermolysis bullosa acquisita, which is caused by the immune system mistakenly attacking the body’s own tissues.
There are four major types of EB based on the site of blister formations within the skin layers: Epidermolysis bullosa simplex (EBS), junctional EB (JEB), dystrophic EB (DEB) and Kindler syndrome.
Within each type of EB, there are many subtypes. To date, researchers have recognized more than 30 subtypes of the condition. These subtypes vary in the severity of symptoms, ranging from mild to severe. The presentation and severity of EB is affected by the specific genetic defects and sometimes can be difficult to classify.
Epidermolysis bullosa simplex (EBS)
In this type, blistering occurs in the upper layer of the skin called the epidermis. It is characterized by a lack of adhesion of the skin directly above the basement membrane (the basal layer). EBS is the most common type of EB, accounting for 70 percent of cases. EBS is milder than other types of EB.
EBS usually is inherited in an autosomal dominant manner, i.e., inheriting a defective gene from a parent is enough to develop the condition.
The blistering may develop either on hands or feet (localized EBS) or all over the body (generalized EBS).
Junctional epidermolysis bullosa (JEB)
In this type, blistering occurs in a skin layer called the lamina lucida within the basement membrane zone, which is situated at the junction between the epidermis and the dermis (lower layer of the skin). JEB is the most severe type of EB and accounts for about 5 percent of cases.
Like EBS, JEB also is inherited in an autosomal recessive manner. However, the condition develops only when the defective gene is inherited from both parents who are EB carriers, but do not show any symptoms themselves.
JEB exists in two forms: The milder form (JEB mild or previously called Herlitz JEB) causes lifelong disability, while the severe form (JEB severe or previously non-Herlitz JEB) usually causes serious blistering and eventually death.
Dystrophic epidermolysis bullosa (DEB)
In this type, blistering occurs in the lamina densa, which is a component of the basement membrane zone between the lamina lucida and the underlying dermis of the skin. DEB accounts for about 25 percent of cases. DEB is characterized by scarring of the healed wounds, resulting in contraction of the joints, fusion of the fingers and toes, contraction of the mouth membranes, and narrowing of the esophagus.
It may be inherited in a recessive or dominant manner.
DEB inherited in a dominant manner is often the less severe form. The severity of the condition may increase with age due to scarring. The recessive form of DEB is more severe and the patients are at a high risk of developing squamous cell carcinoma (an aggressive type of skin cancer).
In this case, blistering may occur at multiple levels within the basement membrane zone, or in skin layers beneath it.
It is rare and characterized by blisters on the hands and feet, altered skin coloring, and damage to the inner lining of body parts such as the mouth, intestines, or eyes.
Epidermolysis bullosa acquisita (EBA)
EBA is a non-genetic autoimmune disease, which is caused by the development of antibodies (proteins that attack foreign substances) against type VII collagen, an essential skin protein. The examination of skin blisters shows antibodies deposited in the basement membrane between the epidermis and dermis. This form of EB is very rare, is not inherited, and usually develops during adulthood.
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