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What Is Epidermolysis Bullosa Simplex?
Epidermolysis bullosa is a group of genetically-caused conditions in which the skin becomes fragile and prone to blistering in response to minor injury or even the mildest irritation. Epidermolysis bullosa simplex (EBS) is one of the groups of epidermolysis bullosa. There are four major forms of EBS:
- Weber-Cockayne. The Weber-Cockayne form of EBS is the mildest of the four forms. Blisters first appears in childhood or young adulthood and primarily affect the feet and hands.
- Koebner. In the Koebner form of EBS, blisters typically arise at or near the time of birth and are widespread on the body.
- Ogna. Like the Koebner form of EBS, the Ogna form is marked by blisters that appear in infancy. These blisters generally affect only the palms and soles of the feet.
- Dowling-Meara. The Dowling-Meara form of EBS is the most severe form. Blistering appears at birth, is very severe and occurs all over the body including in the mouth. Individuals having the Dowling-Meara form of EB usually have finger and toenail problems and experience hyperkeratosis, which is marked by hardening of the palms and soles of the feet.
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Are There Any Known Epidermolysis Bullosa Simplex Mutations?
Researchers have determined that mutations in two genes, designated KRT5 and KRT14, are causative of the Weber-Cockayne, Koebner, and Dowling-Meara forms of EBS. KRT5 and KRT14 encode the proteins keratin 5 and keratin 14 respectively. These keratin proteins, which are tough and fibrous, are found in the outer layer of the skin, known as the epidermis. The purpose of these proteins is to strengthen and provide structure to the epidermis, which is the body's main barrier to the external environment.
Every person has two copies of each one of the KRT5 and KRT4 genes. In most, but not all, cases, mutations in these genes are inherited in autosomal dominant fashion, which means that any person who has even one mutant copy of either one of these genes is likely to develop EBS. Specifically, mutations in the KRT5 and KRT14 genes cause defective keratin 5 and keratin 14 proteins to be synthesized by cells. Whenever defective keratin 5 or keratin 14 protein is made, the epidermis will not be sufficiently strengthened, and therefore it will be easily damaged and very prone to blistering.
The Ogna form of EBS is caused by mutations in a third gene, which is designated PLEC. PLEC encodes the protein plectin, which is needed for the proper attachment of the epidermis to nearby portions of the skin.
Currently, there is no cure for EBS and treatment methods are lacking in that they are mainly aimed at easing discomfort caused by blistering and are not able to reduce the incidence of such blisters. It is hoped that knowledge of the epidermolysis bullosa simplex mutations described above will soon lead to a cure, or at least an optimal treatment, for this often devastating disease.
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Genetics Home Reference, National institutes of Health: http://ghr.nlm.nih.gov/condition/epidermolysis-bullosa-simplex
Mayo Clinic, Epidermolysis Bullosa: http://www.mayoclinic.com/health/epidermolysis-bullosa/DS01015
Medline Plus, National Institutes of Health, Epidermolysis Bullosa: http://www.nlm.nih.gov/medlineplus/ency/article/001457.htm
National Institute of Arthritis and Muscal Skeletal and Skin Diseases, National Institutes of Health, Questions and Answers About Epidermolysis Bullosa: http://www.niams.nih.gov/Health_Info/Epidermolysis_Bullosa/default.asp