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, there are many subtypes. To date, researchers have recognized more than 30 EB subtypes, which vary in the severity of symptoms, ranging from mild to severe. The presentation and severity of EB are affected by the specific genetic defects causing the disease, and 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 generally milder than other types of EB, although the blistering is painful and easily compounded by rubbing.
EBS usually is inherited in an autosomal dominant manner, meaning that a defective gene inherited 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 (upper layer of the skin) and the dermis (lower layer). 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 three forms: Herlitz JEB, a very severe form of EB that can cause serious blistering internally and externally, and is often deadly within early years of life; non-Herlitz JEB, where blistering may be mild or severe, but can cause life-long pain and be disabling; and JEB with associated pyloric atresia, a severe form
In this type of EB, blistering may occur at multiple levels within the basement membrane zone, or in skin layers beneath it.
This syndrome is rare within this disease, and characterized by blisters on the hands and feet, altered skin coloring, and damage to the inner lining of areas such as the mouth, intestines, or eyes.
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 the 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. But severity can increase with age due to scarring, contraction and damage to skin tissue.
The recessive form of DEB is more severe, and patients are at a high risk of developing squamous cell carcinoma (an aggressive type of skin cancer).
Epidermolysis bullosa acquisita (EBA)
EBA is a non-genetic autoimmune disease, caused by the development of antibodies (proteins that attack foreign substances) against type VII collagen, an essential skin protein. An examination of skin blisters will show 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.