Blistering Skin Disorders

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Overview

Epidermolysis bullosa (EB) is a term that refers to a group of inherited disorders characterized by blisters that occur spontaneously or develop as the result of pressure or friction. More than a dozen subtypes have been described. However, there are three main categories: simplex, junctional, and dystrophic, depending on the presence or absence of scarring and the level of separation and breakage within the skin.

In epidermolysis bullosa simplex, the level of separation ( and hence blister formation ) occurs within the top layer of the skin (epidermis), and scar formation does not occur. In junctional EB, the split occurs at the junction of the epidermis and the middle portion of the skin (dermis), and mild scarring can be seen. With dystrophic EB, the split and blister formation is deeper, and there can be extensive scarring. An acquired form, epidermolysis bullosa acquisita (EBA), occurs in adulthood and is usually associated with another disease, such as diabetes mellitus, tuberculosis, or colitis. Blisters usually develop on the hands and feet but can appear anywhere on the body, and there is scarring.

Mild varieties of epidermolysis bullosa may be seen in as many as 1 in 50,000 births; severe forms may occur at the rate of 1 in 500,000 births.

Causes

Epidermolysis bullosa can be inherited both in a dominant (the patient has a 50:50 chance of getting it from a single affected parent) or recessive pattern (one affected gene needs to be present from both parents). The inherited defect causes a weakening in various parts of the skin structure, resulting in skin that is more fragile and susceptible to internal splitting and blister formation.

The closely related form, epidermolysis bullosa acquisita, displays evidence of immune dysfunction (i.e., the patient's own immune system attacks the body) and possible genetic transmission.

Signs and Symptoms

Epidermolysis bullosa simplex can be seen both as a localized or generalized variant. When localized, it affects the palms and soles, and usually presents in adolescence or early adulthood. It may not manifest until the skin is subjected to a high degree of friction, such as with athletic or military training. Excessive sweating often is present.

Generalized epidermolysis bullosa simplex usually occurs at birth or in early infancy, with blisters most commonly on the hands, feet, and extremities. Blisters can be seen in areas subjected to friction, especially when the child begins to crawl and becomes more active. Heat and trauma can exacerbate the disorder. The condition usually improves at puberty.

Junctional EB presents at birth. Its most severe form (Herlitz variant) can be fatal. While some patients survive to adulthood, 50% die before the age of 2. Blisters and erosions (unroofed blisters) are seen on the skin and oral mucous membranes. There can be stomach problems, distinct involvement of the cuticles and fingertips, occasionally leading to loss of the nails, and the teeth may be abnormal. Those affected typically are severely stunted in growth.

In nonlethal junctional EB, blistering is seen at birth. Involvement of the nails may be present as well. While mucous membrane involvement can be seen, it is usually mild. Normal growth and life span are expected.

Dystrophic EB can be seen in both a recessive or dominant form; the dominant form is less severe. In the dominant form, blisters generally appear at or shortly after birth. Growth is unaffected and there is little or no involvement of the hair and teeth. The disease tends to improve with age, and scarring is much less severe. Mild mucous membrane involvement is seen in 20% of patients. The nails usually are thickened and sometimes absent.

In the recessive variant, most blisters occur at the site of trauma or pressure. There is widespread severe scarring and deformities, as well as extensive mucous membrane involvement. The areas of most severe disease include the hands, feet, elbows, and knees. With repeated blistering, thickened scar tissue forms and causes contractures of the joints that restrict mobility. The fingers and toes may be bound together in mitten- or socklike sacs. This form also causes retarded growth and development, with abnormalities of the teeth and hair. The eyes often are affected, as well as the vocal cords, resulting in hoarseness or difficulty speaking. The teeth often are deformed and susceptible to severe cavity formation. Complications from this disease range from poor nutrition to secondary infections of the open areas to problems with urination.

Acquired epidermolysis bullosa (EB acquisita) occurs in adulthood and is characterized by blisters on the hands and feet, as well as the elbows, knees, and ears. Scarring is common, as is mucous membrane involvement. The teeth are unaffected.

Treatment

Treatment varies depending on the severity of the disease. Most treatment of epidermolysis bullosa involves preventing trauma and friction, and controlling secondary infections. Large blisters and erosions should be treated with gentle local wound care, such as with petroleum jelly, gauze, and ointments. Vitamin supplements are recommended, particularly if nutrition is compromised. Oral hygiene is important. Plastic surgery can be performed to relieve severe mittenlike deformities and to restore function of the fingers and toes.

Future therapy developments may address the causes of these diseases, such as with protein or gene therapy. Protein therapy may seek to replace a missing protein, resulting in a repaired skin structure. In gene therapy, a normal gene may be delivered, resulting in proper expression of all the skin proteins and a normal skin strength.

Prevention

The disease cannot be prevented because it is inherited. Prevention of secondary bacterial or fungal infections generally focuses on preventing trauma and friction.

Prenatal diagnosis of epidermolysis bullosa in affected families is best assessed by chorionic villus sampling (CVS). This is akin to sampling a placental membrane and can be done as early as 8 to 10 weeks of gestation. Affected adults should discuss the likelihood of genetic inheritance and the risk of passing it on to one's children.

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