What is EB?

EB is a genetic disorder that results in fragility of the skin and, in some cases, other organs. Blisters and/or erosions form as a result of rubbing, trauma or even a simple hug. In some instances of EB, blisters and/or erosions occur spontaneously.

There is no cure for EB. There is only daily wound care, which can be excruciatingly painful and last for several hours. Genetic research and clinical trials are ongoing to find more effective treatments.

Blisters and erosions occur when layers of the skin fail to properly adhere. Normally, the outer layer of the skin, the epidermis, adheres to the deeper layer of skin, the dermis, through the interaction of proteins that form specific microscopic skin structures, including anchoring fibrils, intermediate filaments and hemidesmosomes. Some of these structures are in the middle layer of skin, which sometimes is called the “junction.”

EB Skin Diagram
Image modified and reprinted with permission from eMedicine.com, 2010. 
Available at: http://emedicine.medscape.com/article/1062939-overview.

 

The three major types of EB are defined by the location of the blister in the skin:

A fourth type of EB, known as Kindler syndrome, is classified as “mixed” because blisters may occur at any level: in the epidermis (intraepidermal), within the lamina lucida (junctional) and below the lamina densa (dermal).

Further classification of EB types depends on the mode of inheritance (dominant versus recessive); appearance and localization of blisters and erosions; and absence or presence and degree of severity of additional clinical features, such as nail dystrophy and involvement of internal organs such as the esophagus and trachea. 

In general, it may be impossible to predict the subtype of EB in a newborn or infant suspected of having EB based on clinical features alone. Skin biopsy for electron microscopy and immunoepitope mapping are the first steps in the diagnosis of EB. These methods usually can suggest the subtype of EB. Immunoepitope mapping allows for more precise localization of the blister to the epidermis, dermal-epidermal junction or dermis, and may also allow for identification of the specific protein that is missing or present in reduced quantity.

Definitive diagnosis of the specific subtype of EB generally relies on genetic testing to identify confirmatory mutation(s) in one of the 10 genes associated with EB. In some patients, no genetic mutation can be identified, and it is possible that other genes also result in EB when mutated. In some cases, identification of the involved mutation(s) also can help to predict the severity of blistering and associated complications. As genetic researchers continue to study Epidermolysis Bullosa, more is learned about the disorder and associated findings.