Epidermolysis bullosa (EB)

Epidermolysis bullosa (EB)

Definition

Epidermolysis bullosa is a group of skin conditions whose hallmark is blistering in response to minor injury, heat, or friction from rubbing or scratching. There are three main types of epidermolysis bullosa, with numerous subtypes. Most are inherited. Most types of epidermolysis bullosa initially affect infants and young children, although some people with mild forms of the condition don't develop signs and symptoms until adolescence or early adulthood. Some infants are born with blisters. Mild forms of epidermolysis bullosa may improve with age, but severe forms may cause serious complications and can be fatal. There's no cure for epidermolysis bullosa. Treatment depends on the severity, but often is aimed at preventing pain, infection and other complications.

Symptoms

The primary indication of epidermolysis bullosa is the eruption of fluid-filled blisters (bullae) on the skin, most commonly on the hands and feet in response to friction. Blisters of epidermolysis bullosa typically develop in various areas, depending on the type. In mild cases, blisters heal without scarring. Depending on the type of the condition, blistering may be present at birth, appear during infancy or occur during adolescence or early adulthood. The three main types are:

• Epidermolysis bullosa simplex, which usually begins at birth or in early infancy.
• Junctional epidermolysis bullosa, which generally begins at birth and is usually severe.
• Dystrophic epidermolysis bullosa, which generally begins at birth or in early childhood.
  

Causes

Your skin comprises an outer layer (epidermis) and an underlying layer (dermis). The area where the layers meet is called the basement membrane zone. Where blisters develop depends on the type of epidermolysis bullosa. In most cases, epidermolysis bullosa is inherited. Researchers have identified more than 10 genes involved with skin formation that, if defective, may cause a type of epidermolysis bullosa. It's also possible to develop epidermolysis bullosa as a result of a random mutation in a gene that occurred during the formation of an egg or sperm cell.
Epidermolysis bullosa simplex

In epidermolysis bullosa simplex, the most common and generally mildest form, the faulty genes are those involved in the production of keratin, a fibrous protein in the top layer of skin. The condition causes the skin to split in the epidermis, which produces blisters. If you have epidermolysis bullosa simplex, it's likely you inherited a single copy of the defective gene from one of your parents (autosomal dominant inheritance pattern). If one parent has the single faulty gene, there's a 50 percent chance their offspring will have the defect.

Junctional epidermolysis bullosa

In this usually severe type of the disorder, the faulty genes are involved in the formation of thread-like fibers (hemidesmosomes) that attach your epidermis to your basement membrane. This gene defect causes tissue separation and blistering in your basement membrane zone. Junctional epidermolysis bullosa is the result of both parents carrying and passing on the defective gene (autosomal recessive inheritance pattern), although neither parent may have the disorder (silent mutation). If both parents have the faulty gene, there's a 25 percent chance their offspring will have the defect and develop the disorder.

Dystrophic epidermolysis bullosa

In this type, whose subtypes range from mild to severe, the faulty genes are involved in the production of a type of collagen, a protein in the fibers that attach your epidermis to your dermis. As a result, the fibers are either missing or nonfunctional. Dystophic epidermolysis bullosa can be either dominant or recessive.