Chapter 6 Mechanobullous disorders
1. What are the mechanobullous disorders?
This is a group of disorders, either inherited or acquired, that result in small blisters (vesicle) or large blisters (bulla) that form after trauma to the skin. The most common acquired lesion would be a typical blister that one can develop on a foot after the skin rubs on a shoe or boot. The most common inherited mechanobullous disorders are those that fall into the category of epidermolysis bullosa (EB). Vesicles and bullae develop in these individuals with very minor trauma. The remaining portion of this chapter will deal with EB and its complications.
2. Do all of the blisters that form in EB develop in the same layer of the skin?
No. Depending on the type of EB there are three basic levels of separation within the skin. The two basic layers of skin are the epidermis and dermis. The junction between these two layers contains important structural proteins and is called the dermal–epidermal junction (DEJ) (Fig. 6-1). Separation due to trauma may occur in any one of these three anatomic sites.
Figure 6-1. Layers of the skin with major sites of splitting in epidermolysis bullosa (EB).
(Courtesy of James E. Fitzpatrick, MD.)
Key Points: Heritable Blistering Disorders
1. Epidermolysis bullosa is an inherited group of disorders characterized by genetic defects of structural proteins needed for the normal attachment and integrity of the epidermis.
2. There are four major subtypes with different ultrastructural localization of the blister: EB simplex (epidermal cleavage plane), junctional EB (cleavage plane between epidermis and dermis), dystrophic EB (cleavage plane in superficial dermis), and Kindler’s syndrome (with a mixed split of both epidermis and dermis).
3. How is EB classified, and what are the major modes of inheritance?
In the past, there were three major categories of EB, depending on the level of the blister, and numerous subtypes within each category. In 2008, the Third International Consensus Meeting on Diagnosis and Classification of EB was published. In this manuscript, there was an attempt to simplify classification and eliminate misleading terms and acronyms. EB is now divided into four major categories:
4. Describe the clinical findings in EB simplex.
In the common localized variety, the presentation is that of easy blistering noted on the hands and feet. These individuals may go undiagnosed until they are placed in a situation that generates increased pressure to these surfaces, such as marching in the military (Fig. 6-2). The generalized form is also usually present at birth, but, on rare occasions, it may not appear until 6 to 12 months of age in areas of trauma. The affected areas generally heal without scarring. In the simplex forms, generally the skin is the only thing affected; however, in the more severe forms of generalized simplex, they can have oral mucosa involvement and, on rare occasions, have esophageal strictures. The good news is that in some of the severe forms of generalized simplex EB the blistering tends to improve as the child ages. This is true for both the intraoral and cutaneous lesions.
