- A spectrum of rare genodermatoses in which a disturbed coherence of the epidermis and/or dermis leads to blister formation following trauma. Hence, the designation mechano-bullous dermatoses.
- Disease manifestations range from very mild to severely mutilating and even lethal forms that differ in mode of inheritance, clinical manifestations, and associated findings.
- Classification based on the site of blister formation distinguishes three main groups: epidermolytic or EB simplex (EBS), junctional EB (JEB), and dermolytic, or dystrophic, EB (DEB).
- In each of these groups there are several distinct types of EB based on clinical, genetic, histologic, and biochemical evaluation.
Based on level of cleavage and blister formation there are three main types:
- Epidermolytic. Cleavage occurs in keratinocytes: EB simplex (EBS)
- Junctional. Cleavage occurs in basal lamina: junctional EB (JEB)
- Dermatolytic. Cleavage occurs in most superficial papillary dermis: dermolytic, or dystrophic, EB (DEB)
In each of these groups there are several distinct types of EB based on clinical, genetic, histologic/electronmicroscopic, and biochemical evaluation (Table 6-1). Only the most important are discussed here.
Table 6-1 Classification of Epidermolysis Bullosa |Favorite Table|Download (.pdf)
Table 6-1 Classification of Epidermolysis Bullosa
Level of Separation
EB with muscular dystrophy
EB with pyloric atresia
Generalized atrophic benign
Ectodermal dysplasia-skin fragility
The overall incidence of hereditary EB is placed at 19.6 live births per 1 million births in the United States. Stratified by subtype, the incidences are 11 for EBS, 2 for JEB, and 5 for DEB. The estimated prevalence in the United States is 8.2 per million, but this figure represents only the most severe cases as it does not include the majority of very mild disease going unreported.
Etiology and Pathogenesis
Molecules involved are listed in Table 6-1 and localization in the tissue and sites of cleavage are shown in 5200895.