Epidermolysis bullosa simplex (EBS) is the most common form of the rare genetic skin disorder known as epidermolysis bullosa. Typically appearing in infancy or early childhood, EBS ranges from mild blistering that is usually localized to the hands and feet, to more severe and generalized blistering of the skin.
Causes of EBS
EBS is caused by mutations in either the KRT5 or KRT14 gene that prevents keratin proteins from assembling into strong networks in the outer layer of the skin (the epidermis). This protein, which also makes up hair and nails, give the skin its structure and hold the different layers together; without keratin, the epidermis is fragile and easily damaged. With friction or the slightest trauma, the skin blisters.
EBS is inherited in an autosomal dominant pattern, meaning that a single copy of the defective gene from either parent is sufficient to cause the disease.
Types and symptoms
There are four major subtypes of EBS:
- Localized EBS, formerly called Weber-Cockayne type, is marked by blisters typically confined to hands, feet, and areas where the skin has been rubbed or injured. This form is mild, and usually begins in childhood, although it can manifest in adolescence and early adulthood.
- Generalized EBS, formerly called Köbner type, has blisters that are widespread, occurring across the body. This form is not considered severe, but is not localized. The disease may involve the mucus membranes, and fingernails and toes. It usually is evident at birth or appears in early infancy.
- EBS with mottled pigmentation is characterized by fragile skin and easy blistering at birth or in infancy, varied pigmentation (darker and lighter patches) throughout the body, keratosis (thickened skin) on the palms of the hands and the soles of the feet, and abnormal nail growth. The differently colored skin usually disappear with age, but the keratosis can be a problem throughout adulthood.
- Generalized severe EBS, or Dowling-Meara type, is the most severe type of this disease and present at birth. It is characterized by widespread and severe blistering all over the body, and sometimes in the linings of the nose, mouth, esophagus, and intestines. Hemorrhagic (bleeding) blisters and clusters of small blisters, called milia, also occur. This subtype can affect the muscles as well, and progressive keratosis (skin hardening) on the palms and soles can cause significant pain throughout life. Although symptoms may improve in childhood, this form of EBS is a serious disease of infancy and early childhood, and can be life-threatening.
Treatment mainly consists of avoiding activities that damage the patient’s delicate skin. Creams and moisturizers are used to manage skin health, and to help control and prevent infections that may result from the open blisters. Aluminum chloride and other medicines can be used to prevent blisters from forming; keratolytics and other softening agents on hardened skin of the palms and soles may prevent tissue from thickening and cracking.
Antibiotics or silver-impregnated dressings or gels may be used to treat infections.
Key is ensuring that the patient eats and drinks properly, as blisters can accelerate dehydration. Blisters in the patient’s mouth and esophagus can make it painful to eat and drink and special care must be given.
Gene therapies are being tested that may reduce the effects of EBS, possibly stop its progression, or cure it. At present, however, no disease-modifying treatment or cure for epidermolysis bullosa simplex exists.
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