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Epidermolysis Bullosa
Epidermolysis bullosa is the name given
to a group of genetically determined disorders, which are characterized by an
excessive susceptibility of the skin and mucosae to separate from the underlying
tissues following mechanical trauma. The individual diseases vary in their impact from relatively
minor disability (e.g. limitation of walking distance because of blistering of
the feet), to death in infancy.
There are three broad categories of
Epidermolysis bullosa:
Epidermolysis bullosa simplex,
dystrophic Epidermolysis bullosa and junctional Epidermolysis bullosa.
Within each of these categories, there are several sub-types which are
clinically, and probably genetically, distinct.
Types and Causes
EB Simplex – A group of inherited
disorders characterized by mechanically induced blistering occurring within the
epidermis itself, as a result of lysis of the basal keratinocytes (breakdown of
epidermal skin cells). There are
several established variants, of which the following are the most important:
 | Weber-Cockayne
type – Epidermolysis bullosa localized to the hands and feet. |
| Koebner
type – generalized Epidermolysis bullosa simplex. |
| Dowling-Meara
type – Epidermolysis bullosa simplex herpetiformis. |
In addition, there are a number of rarer
variants which are encountered from time to time. The prevalence of the different forms of Epidermolysis
bullosa simples can only be estimated. Weber-Cockayne
type is probably 10-20 cases per million population, Koebner is rarer, possibly
about 2 cases per million and Dowling-Meara appears to be in the region of 5-10
cases per million. Almost all forms
of Epidermolysis bullosa simplex are inherited as autosomal dominant traits,
although some rare forms are inherited as autosomal recessive traits.
People with the generalized and the localized forms almost always have
extensive family histories of the condition.
Dystrophic Epidermolysis bullosa
A group of inherited disorders characterized
by mechanically induced blistering occurring immediately below the
lamina densa of the basement membrane zone. These disorders derive the name dystrophic from the tendency
of the blisters to heal with atrophic scarring.
Dystrophic Epidermolysis bullosa may be inherited as an autosomal
dominant or an autosomal dominant or an autosomal recessive trait.
In general, it tends to be most severe when inherited as a recessive, and
mildest when inherited as a dominant, but there is considerable clinical
overlap. There are few data to
indicate the prevalence of dystrophic Epidermolysis bullosa.
A recent study in Scotland indicated an estimated prevalence of 21.4
cases per million.
Junctional Epidermolysis bullosa
A group of inherited disorders characterized
by mechanically induced blistering occurring within the basement
membrane at the level of the lamina lucida.
There are three broad types of junctional Epidermolysis bullosa:
| Lethal
junctional Epidermolysis bullosa – in which death is probable within the
first two years of life. |
| Benign
junctional Epidermolysis bullosa – in which many people will survive into
adult life. |
| Junctional
Epidermolysis bullosa with pyloric atresia. |
Because most affected individuals die
early in life, the incidence of junctional Epidermolysis bullosa is particularly
difficult to ascertain. It is
estimated that the incidence of new cases is approximately the same as for
dystrophic Epidermolysis bullosa, i.e. around 20 per million births.
To date, all types of junctional Epidermolysis bullosa have been
transmitted as autosomal recessive traits.
Symptoms and Treatments
Due to the large number of different
forms of Epidermolysis bullosa with greatly differing symptoms and prognoses, it
is unwise to try to describe these in any detail here. Broadly, the common features of the condition relate to
blistering of the skin and mucosa at the slightest friction.
In some forms the blistering is confined to particular areas of the body,
such as the hands and feet. In
others the blistering can affect all of the body.
The blistered areas in some forms of Epidermolysis bullosa heal normally,
in others healing is accompanied by scarring.
In view of this, specific information
should always be obtained from a competent clinician who will be able to relate
the information given to the precise form of Epidermolysis bullosa that the
person has.
any questions email us at doctor@skinpatient.com
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