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Epidermolysis Bullosa

Epidermolysis Bullosa

Definition

Epidermolysis bullosa (EB) is a group of rare inherited skin diseases that are characterized by the development of blisters following minimal pressure to the skin. Blistering often appears in infancy in response to simply being held or handled. In rarer forms of the disorder, EB can be life-threatening. There is no cure for the disorder. Treatment focuses on preventing and treating wounds and infection.

Description

Epidermolysis bullosa has three major forms and at least 16 subtypes. The three major forms are EB simplex, junctional EB, and dystrophic EB. These can range in severity from mild blistering to more disfiguring and life-threatening disease. Physicians diagnose the form of the disease based on where the blister forms in relation to the epidermis (the skin's outermost layer) and the deeper dermis layer.

The prevalence of epidermolysis varies among different populations. A study in Scotland estimated the prevalence to be one in 20,400. Researchers in other parts of the world estimate the prevalence to be one in 100,000. This variance is due to the variability of expression. Many cases of epidermolysis bullosa are often not accurately diagnosed and thus, are not reported.

Causes and symptoms

EB can be inherited as the result of a dominant genetic abnormality (only one parent carries the abnormal gene) or a recessive genetic abnormality (both parents carry the abnormal gene).

EB simplex results from mutations in genes responsible for keratin 5 and 14, which are proteins that give cells of the epidermis its structure. EB simplex is transmitted in an autosomal dominant fashion.

Dystrophic EB is caused by mutations in genes for type VII collagen, the protein contained in the fibers anchoring the epidermis to the deeper layers of the skin. The genetic mutations for junctional EB are found in the genes responsible for producing the protein Laminin-5. Dystrophic EB is an autosomal disorder and will only result if both parents transmit an abnormal gene during conception.

EB simplex, the most common form of EB, is the least serious form of the disease. In most affected individuals, the blisters are mild and do not scar after they heal. Some forms of EB simplex affect just the hands and feet. Other forms of EB simplex can lead to more widespread blistering, as well as hair loss and missing teeth. Recurrent blistering is annoying but not life threatening.

The second, or junctional, form of EB does not lead to scarring. However, skin on the areas prone to blistering, such as elbows and knees, often shrinks. In one variation of junctional EB, called gravis junctional EB of Herlitz, the blistering can be so severe that affected infants may not survive due to massive infection and dehydration.

The third form of EB, dystrophic EB, varies greatly in terms of severity, but more typically affects the arms and legs. In one variation, called Hallopeau-Siemens EB, repeated blistering and scarring of the hands and feet causes the fingers and toes to fuse, leaving them dysfunctional and with a mitten-like appearance.

Diagnosis

Physicians and researchers distinguish between the three major subtypes of EB based on which layer of the epidermis separates from the deeper dermis layer of the skin below. Patients suspected of having EB should have a fresh blister biopsied for review. This sample of tissue is examined under an electron microscope or under a conventional microscope using a technique called immunofluorescence, which helps to map the underlying structure.

Knowing that a family member has EB can help establish the diagnosis, but it is possible that parents or siblings will show no sign of the disease, either because it is caused by a new genetic mutation, or because the parents are carriers of the recessive trait and do not display the disease.

KEY TERMS

Collagen The main supportive protein of cartilage, connective tissue, tendon, skin, and bone.

Dermis The layer of skin beneath the epidermis.

Epidermis The outermost layer of the skin.

Keratin A tough, nonwater-soluble protein found in the nails, hair, and the outermost layer of skin. Human hair is made up largely of keratin.

Treatment

The most important treatment for EB is daily wound care. Because the skin is very fragile, care must be taken to be certain that dressing changes do not cause further damage. Tape should not be applied directly to skin and bandages should be soaked off. Infection is a major concern, so a topical antibiotic, such as bacitracin, mupirocin, or sulfadiazine, should be routinely applied. Among persons with recessive dystrophic EB, the anticonvulsant phenytoin is sometimes effective because it decreases production of an enzyme that breaks down collagen.

Prognosis

The prognosis of EB varies depending on the subtype of the disease. Individuals with EB simplex can live long, fulfilling lives. The severity of the junctional and dystrophic forms of EB can vary greatly. Infants affected with some forms of the disease often do not survive infancy; other forms can lead to severe scarring and disfigurement.

Resources

BOOKS

Fine, Jo-David, et al. Epidermolysis Bullosa: Clinical,Epidemiologic, and Laboratory Advances, and the Findings of the National Epidermolysis Bullosa Registry. Baltimore: Johns Hopkins Univ Press, 1999.

Fitzpatrick, Thomas B., Richard A. Johnson, Wolff Klaus, and Dick Suurmond. Color Atlas and Synopsis of Clinical Dermatology. 4th ed. NewYork: McGraw-Hill, 2000.

Mallory, S.B. Atlas of Pediatric Dermatology. Pearl River, NY: Parthenon, 2001.

PERIODICALS

Cotell, S., N. D. Robinson, and L. S. Chan. "AutoimmuneBlistering Skin Diseases." American Journal of Emerging Medicine 18, no. 3 (2000): 288-99.

ORGANIZATIONS

American Academy of Dermatology. PO Box 4014, 930 N. Meacham Rd., Schaumburg, IL 60168-4014. (847) 330-0230. Fax: (847) 330-0050. http://www.aad.org.

OTHER

Dermatology Online Atlas. http://www.dermis.net/doia/diagnose.asp?zugr=d&lang=e&diagnr=757320&topic=t.

Dystrophic Epidermolysis Bullosa Research Association International. http://debra-international.org/index1.htm.

Epidermolysis Bullosa Medical Research Foundation. http://www.med.stanford.edu/school/dermatology/ebmrf/.

Oregon Health Sciences University. http://www.ohsu.edu/cliniweb/C17/C17.800.865.410.html.

University of Iowa College of Medicine. http://tray.dermatology.uiowa.edu/EBA-001.htm.

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epidermolysis bullosa

epidermolysis bullosa (EB) (epi-der-mol-i-sis buul-oh-să) n. any one of a group of genetically determined disorders characterized by blistering of skin and mucous membranes. In the simple forms the blistering is induced by injury. In the more serious (dystrophic) forms the blistering may occur spontaneously; some of the dystrophic forms of the disease are fatal.

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