Epidermolysis bullosa (EB) is a rare skin disease characterized by tearing and blistering at the slightest touch. It usually is evident at birth, but forms with milder symptoms can become apparent later in life.
EB has four major types based on the site of blister formations within the skin layers: epidermolysis bullosa simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler syndrome.
A non-genetic type, called epidermolysis bullosa acquisita, is caused by the immune system mistakenly attacking a key skin protein.
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 its specific cause, most often gene mutations, and can be difficult to classify.
Epidermolysis bullosa simplex (EBS)
In EBS, blistering occurs in the epidermis, the upper layer of the skin. It is characterized by a lack of adhesion in this layer —directly above the basement membrane — due to mutations that prevent the keratin proteins from forming strong networks in the epidermis. EBS is the most common type of EB, accounting for 70% of all cases. It is generally milder than other types of EB, although the blistering is painful and easily accentuated by rubbing.
EBS is usually is inherited in an autosomal dominant manner, meaning that a defective gene inherited from one parent is enough to develop the disease.
There are four major types of EBS: localized EBS, where blistering typically develops on hands or feet; generalized EBS, in which blisters occur all over the body; EBS with mottled pigmentation, which is characterized by darker patches of skin on the limbs and trunk; and severe EBS, marked by widespread and extreme blistering across the body.
Junctional epidermolysis bullosa (JEB)
Blistering in JEB occurs within the basement membrane of the skin, a membrane that lies between the epidermis and the dermis (lower skin layer) and keeps the two connected. JEB is one of the most severe types of EB.
JEB is inherited in an autosomal recessive manner. This means the condition develops only when the defective gene is inherited from both biological parents, who are EB carriers and possibly do not know this, as they would not have symptoms themselves.
JEB exists in two main forms: generalized severe JEB, characterized by serious internal and external blistering, and usually associated with a poor life expectancy; and non-generalized severe JEB, a milder form in which a normal lifespan is possible.
Other forms of JEB include localized JEB, JEB with pyloric atresia, JEB inversa, late-onset JEB, and JEB with interstitial lung disease (associated with scarring) and nephrotic syndrome (kidney damage).
Dystrophic epidermolysis bullosa (DEB)
In DEB, blistering occurs as a result of very fragile connections between skin layers, which can make them susceptible to blisters and tearing with the slightest movement. DEB can be milder or severe, depending on the extent of the deficiency in type VII collagen, a protein that connects the different layers of the skin and is affected by DEB-causative mutations.
DEB accounts for about 25% of all cases, making it the second most common form of this disease. It is characterized by the scarring of the healed wounds, resulting in contraction of the joints, membranes of the mouth, fusion of the fingers and toes, and narrowing of the esophagus.
This EB type can be inherited in a recessive or dominant manner. With dominant inheritance, DEB is often less severe. But its severity can increase as a person ages due to scarring, fused fingers, 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, a type of skin cancer.
This syndrome is very rare within this disease, with about 250 cases reported to date worldwide.
In this type of EB, blistering may occur at multiple levels within the basement membrane zone (the layer linking the epidermis to the dermis), or in skin layers beneath it.
Kindler syndrome is 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.
The disease, caused by mutations in the FERMT1 gene, is inherited in an autosomal recessive pattern.
Epidermolysis bullosa acquisita (EBA)
EBA is a non-genetic autoimmune disease, caused by the development of antibodies (proteins that typically attack foreign substances) against type VII collagen. An examination of skin blisters will show antibodies deposited in the basement membrane between the epidermis and dermis. This form of EB is quite rare and generally affects adults.
EBA has also been found in some family members, suggesting that genetics may contribute to the disorder.
People with EBA show chronic inflammation, as well as blistering and scarring of the skin and the mucous membranes that line body cavities and canals, including the nose, mouth, lungs, stomach, and bladder.
EBA can be classified as non-inflammatory and inflammatory. Inflammatory EBA may be divided into four subtypes based on its similarity to other blistering conditions: bullous pemphigoid, linear IgA disease, mucous membrane pemphigoid, and Brunsting-Perry pemphigoid.
Last updated: July 29, 2021
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