The term epidermolysis bullosa (EB) encompasses a group of genetic mechanobullous disorders. They are characterized by fragile skin and the tendency to develop noninflammatory blisters and erosions on skin and mucous membranes following trivial trauma. Internal organ involvement may also occur. The incidence of all subtypes of heritable EB is 19.6 live births per one million births in the United States. EB is classified based on the level of blister formation and is divided into three distinct groups: epidermolytic or EB simplex, junctional EB, and dermolytic or dystrophic EB.
There are at least eleven different forms of epidermolysis bullosa simplex (EBS), seven of which are dominantly inherited. EBS is characterized by the heat sensitive formation of vesicles and bullae, typically beginning in infancy and childhood. Lesions do not scar. Blistering is due to mutations in the genes coding for keratins 5 and 14 which are located in the basal epidermal cells. However, rare variants demonstrate abnormalities in other basement membrane structures. On histologic evaluation, the blister is intraepidermal with the level of separation at the mid basal level on electron microscopic exam. Immunomapping typically demonstrates diminished or absent keratins 5 and 14.
There are at least 6 subtypes of junctional epidermolysis bullosa (JEB). All are inherited in an autosomal recessive manner and are typically present at birth or in infancy. All demonstrate cutaneous blisters, usually generalized, that heal with atrophic scars. In addition, all patients have some evidence of dystrophy or absence of nails, involvement of the teeth with enamel defects, and scalp involvement. Internal organs may be involved in the more severe phenotypes. Blistering is typically due to mutations/absence of laminin 5. However, some variants have abnormalities in additional basement membrane components such as alpha 6 beta 4 integrin and BPAG 2 which both associate with laminin 5. On histopathologic and electron microscopic exam, blister formation is within the lamina lucida. Immunomapping typically demonstrates diminished or absent laminin 5 or other anchoring filament associated proteins as mentioned above.
There are four major subtypes of dystrophic epidermolysis bullosa (DEB) and these are divided into two groups: dominant DEB and recessive DEB. These disorders usually present at birth and are characterized by blisters that heal with scarring and milia formation. Nail and oral involvement is common. In the dominant form, patients typically have a normal lifespan while in the recessive form, internal organ involvement is common and lifespan is decreased. All are due to mutations in the anchoring fibrils (type VII collagen). On histopathologic exam, blister formation is subepidermal and electron microscopic exam demonstrates a split in the sublamina densa zone. Immunomapping typically demonstrates diminished or absent type VII collagen.
For all of the EB variants, patients should be advised to avoid trauma. Treatment is primarily supportive. Proper wound manmagement and infection control measures should be in place. Genetic counseling is essential and fetal skin biopsy techniques and fetoscopy are now available for prenatal diagnosis.