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Mechanobullous Disorders

»	What are the mechanobullous disorders?
»	Do all of the blisters that form in EB develop in the same layer of the skin?
»	How is EB classified, and what are the major modes of inheritance?
»	Describe the clinical findings in EB simplex.
»	Is the cause of EB simplex known?
»	What are the clinical findings in junctional EB?
»	Is the cause of junctional EB known?
»	What are the clinical findings in dystrophic EB?
»	Is the cause of dystrophic EB known?
»	What is Kindler’s syndrome?
»	Can a definitive diagnosis of the various EB types be made on clinical presentation?
»	Are there any treatments for the mechanobullous disorders?
»	Are prenatal diagnostic techniques useful for this group of disorders?

Is the cause of EB simplex known?

Fig. 6.3 Generalized EB simplex demonstrating generalized truncal blistering.

Yes. In the vast majority of cases simplex EB is due to a mutation in either keratin 5 or 14 (Fig. 6-3). Keratins are structural proteins within keratinocytes that give the keratinocytes their shape and size, similar to the frame in a house. Keratins 5 and 14 are expressed in the basal layer of the epidermis, which is why the split is in the epidermis in EB simplex. There are rare forms of EB simplex that involve other structural proteins within the epidermis, such as plakophilin, desmoplakin, plectin, and integrins. Of interest is the simplex form of EB involving the protein plectin. Plectin is also important in skeletal muscle and individuals affected by the plectin form of EB simplex develop muscular dystrophy, usually after puberty.

Charlesworth A, Gagnous-Palacios L, Bonduelle M, et al: Identification of a lethal form of epidermolysis bullosa simplex associated with a homozygous mutation in plectin, J Invest Dermatol 121:1344–1348, 2003.