Epidermolysis bullosa

Overview
Epidermolysis Bullosa (EB) is a rare genetic disease characterized by the presence of extremely fragile skin and recurrent blister formation, resulting from minor mechanical friction or trauma. The condition was brought to public attention in the UK through the Channel 4 documentary The Boy Whose Skin Fell Off, chronicling the life and death of English sufferer Jonny Kennedy.

Forms
There are three main forms of inherited EB. These different subtypes are defined by the depth of blister location within the skin layers, and the location of the dissolution of the skin.

EB Simplex (EBS) -- ABOVE the basement membrane

 * See main article at Epidermolysis Bullosa simplex.

Blister formation of EB Simplex is within the basal keratinocyte of the epidermis. Sometimes EB simplex is called epidermolytic. There are four subtypes of EBS:


 * 1) EBS - Weber-Cockayne (EBS-WC)
 * 2) EBS - Koebner (EBS-K)
 * 3) EBS - Dowling-Meara (EBS-DM) -- caused by missense mutation in KRT5 (E477K) or one of two missense mutations in KRT14 (R125C and R125H)
 * 4) EBS - Mottled Pigmentation (EBS-MP) - caused by one missense mutation in KRT5 (I161S) or by missense mutations in the plectin gene (Koss-Harnes et al., 1997;Koss-Harnes et al., 2002).

Junctional EB (JEB) -- THROUGH the basement membrane
Condition characterized by spontaneous blistering of the skin and mucous membranes at the level of the lamina lucida within the basement membrane zone. Condition is caused by defects in the structures of laminin 5, laminin 6, collagen XVII, proteins that contribute to the cohesion of the dermis and epidermis. A severe form of the disease, JEB gravis is often fatal early in life. Death occurs as a result of epithelial blistering of the respiratory, digestive and genitourinary systems.

Dystrophic EB (DEB) -- UNDER the basement membrane

 * See main article at Epidermolysis Bullosa dystrophica.

Dystrophic EB (DEB) forms which can lead to scarring occur in a deeper tissue level; the sub-lamina densa region (the beneath the lamina densa) within the upper dermis.

Layman's Terms
The skin has two layers; the outer layer is called the epidermis and the inner layer the dermis. In normal individuals there are "anchors" between the two layers that prevent them from moving independently from one another. In people born with EB the two skin layers lack the anchors that hold them together, and any action that creates friction between the layers (like rubbing or pressure) will create blisters and painful sores. Sufferers of EB have compared the sores to third-degree burns.

Epidemiology
An estimated 50 in 1 million live births are diagnosed with EB, and 9 in 1 million are in population. Of these cases, approximately 92% are EBS, 5% are DEB, 1% are JEB, and 2% are unclassified. Carrier frequency ranges from 1 in 333 for Junctional, to 1 in 450 for Dystrophic. Carrier frequency for Simplex is not indicated in this article, but is presumed to be much higher than JEB or DEB.

The disorder occurs in every racial and ethnic group throughout the world and affects both genders.